Rich Barton is one busy guy. An ex-Microsoft (MSFT) exec and a founder of Expedia (EXPE), he’s currently chairman and CEO of Zillow.com, the most voyeuristically interesting Web site in the real estate business. On the side he’s also a director of Netflix (NFLX) and the children’s-advocacy group Common Sense Media; a partner with some Seattle buddies in a $10-million, quant-jock hedge fund the group plans to expand by taking outside money; a venture partner at Benchmark Capital; oh, and a founder of two new startups, Avvo.com and an unlaunched company called Glassdoor.

Barton also is disgustingly relaxed, as I learned when he dropped by my office Tuesday morning, mostly to talk about Zillow. If you don’t know Zillow, which is based in Seattle, first read Jeff O’Brien’s rollicking cover story last year in Fortune. It explains how Zillow has attracted a wide audience of titillated homeowners and shoppers who like to check on Zillow’s “Zesstimates” of the value of just about any home in America. To hear Barton tell the tale, the company continues to rock. Unlike every other real estate Web site, Zillow is a pure media company. Its only goal is to sell advertising, and it’s doing that with an increasing drumbeat of ingenious creations. Jeff wrote last year about Zillow’s “Make Me Move” feature, where homeowners edit Zillow’s listing of their own house and then taunt the curious to make them an offer they can’t refuse. Since then the company has added catchy ideas like a mortgage marketplace, where prospective borrowers anonymously post their needs and lenders publicly state their terms. Another new feature is “Dueling Digs.” I’ll just describe it as the Hot or Not of real estate and let you check it out for yourself. (Watch for a related “home improvement” section to be Zillow’s next practical, as opposed to entertaining, site feature.)

So how’s Zillow doing? “It has embedded itself into the process of real estate,” he says, with about the amount of modesty you’d expect from someone with his list of accomplishments. Barton says the company had 5.2 million unique visitors to the site in March, according to internal logs provided by Omniture (OMTR), whose numbers typically are higher than third-party ratings. Two million homes are for sale at Zillow, thanks to the site having won over real estate agents happy to accept its free services. It sports advertisers include homebuilders like Lennar (LEN), Verizon (VZ) (which advertises only to areas it serves with the specific service it is promoting on Zillow), and Deere (DE), for whom Zillow tailored an ad program that appears only on homes whose acreage justifies the purchase of a riding mower. That’s not only freaking smart, it’s a perfect example of the kind of targeted advertising the Web delivers better than any other medium.

Zillow also sells ads the same way everyone else does, through Google’s (GOOG) publisher network, AdSense, as well as with a national sales force. Barton says the 150-person company isn’t profitable yet but that he can “see profitability.” He has raised a total of $87 million from an investor list that includes Benchmark, Technology Crossover Partners, the Boston hedge fund PAR Capital Management, and Legg Mason (LM), whose behind-the-scenes investing guru (and ex-journalist) Randy Befumo has an observer seat on the Zillow board.

As Barton prepares to leave, I do wonder aloud if the housing downturn won’t render Zillow a bit player. Unsurprisingly, he’s ready. “We think people are spending more time online shopping for homes now,” he says, noting that the end of the frantic days of bidding on homes immediately or losing out play to a Web site’s advantage. But what if, I ask, the great homeowning game of the last few decades has played out, if we go back to being a nation of some owners and many renters? “Shelter is primal,” responds the entrepreneur, for whom starting companies clearly is just as ingrained.

As the great credit crisis of 2007-2008 finally begins to lose steam, most people still don’t understand what the heck happened. For good reason. It’s confusing stuff. The terminology is complicated. The people aren’t well known. The pieces move around quickly.

To the rescue comes Roger Lowenstein, author of When Genius Failed and, significantly, a fine article in this past weekend’s New York Times Magazine. In a nutshell, Lowenstein explains methodically, and in some of the simplest declarative sentences you’ll find written in business journalism, how conflicts of interest at the credit-rating agencies — Moody’s (MCO), S&P (MHP) and Fitch — misled investors in mortgage-backed securities.

The conflict is straightforward, and I’ve written about it here before: The agencies make most of their money from fees paid by bond issuers and their banks rather than from the investors who rely on the ratings. Lowenstein neatly dismisses the credit agencies’ explanation that they did the best they could with the information they had at their disposal. In a pivotal passage, Moody’s walks readers through an actual portfolio of subprime mortgages that was packaged by an investment bank and rated by Moody’s. The actual names are obscured as “Subprime XYZ,” which is how Moody’s was willing to share the illustrative example with Lowenstein. Consider this passage:

The loans in Subprime XYZ were issued in early spring 2006 — what would turn out to be the peak of the boom. They were originated by a West Coast company that Moody’s identified as a “nonbank lender.” Traditionally, people have gotten their mortgages from banks, but in recent years, new types of lenders peddling sexier products grabbed an increasing share of the market. This particular lender took the loans it made to a New York investment bank; the bank designed an investment vehicle and brought the package to Moody’s.

Moody’s assigned an analyst to evaluate the package, subject to review by a committee. The investment bank provided an enormous spreadsheet chock with data on the borrowers’ credit histories and much else that might, at very least, have given Moody’s pause. Three-quarters of the borrowers had adjustable-rate mortgages, or ARMs — “teaser” loans on which the interest rate could be raised in short order. Since subprime borrowers cannot afford higher rates, they would need to refinance soon. This is a classic sign of a bubble — lending on the belief, or the hope, that new money will bail out the old.

Moody’s learned that almost half of these borrowers — 43 percent — did not provide written verification of their incomes. The data also showed that 12 percent of the mortgages were for properties in Southern California, including a half-percent in a single ZIP code, in Riverside. That suggested a risky degree of concentration.

On the plus side, Moody’s noted, 94 percent of those borrowers with adjustable-rate loans said their mortgages were for primary residences. “That was a comfort feeling,” Robinson said. Historically, people have been slow to abandon their primary homes. When you get into a crunch, she added, “You’ll give up your ski chalet first.”

This shows Moody’s understood full well that the mortgages were all subprime. This means
that, by definition, the mortgage holders had inferior credit, and that a giant percentage didn’t supply documentation to back up their income claims on their mortgage applications. Moody’s and others say they were victims of fraud. Yet they’ve admitted to Lowenstein that they were willing victims of fraud. A final note to Claire Robinson, the veteran Moody’s executive quoted at the end of that passage: People who can’t afford prime mortgages typically don’t have ski chalets.

It’s worth taking a step back here and asking what can be done about the conflict. I met Monday with Bill Hambrecht, the founder of the old Hambrecht & Quist [now part of JPMorgan Chase (JPM)] as well as his current firm, the dutch-auction promoter WR Hambrecht + Co. He told me it’s not simply that the ratings agencies curry favor with the banks. It’s also that the analysts at the agencies, who might make in the neighborhood of $100,000 a year, cozy up to the bankers they meet with because they’re interested in going to work for the banks, where they can earn a lot more money. Hambrecht’s solution: Empower the government to rate bonds, especially if the government requires certain kinds of fund managers to own only officially-rated bonds. Lowenstein, by the way, comes to essentially the same conclusion, though he doesn’t directly advocate a government-run ratings regime.

We had a busy week just last Monday and Tuesday at Fortune’s green business conference in Pasadena, Calif. There’s been a ton of coverage of what went on, especially the launch of an all-electric car, the Think City, in the United States by the Norwegian company Think Global and its North American investing partners, Kleiner Perkins and Rockport Capital. I moderated six panels at the conference, and though it took me a few days to mop up afterward, I thought I’d offer a few thoughts on each. The one comment I heard most frequently at the conference was how pleased the business people there were to find environmentalists willing to have reasonable conversations with them about solutions to the global climate change problem, and, conversely, how excited the enviros were to find so many high-level business types (not just the ghettoized “corporate and social responsibility” types) taking the conversation so seriously — all under the Fortune banner.

1. Think. What was particularly cool about the Think launch is that the Think crowd, let by CEO Jan-Olaf Willums, brought two cars with them to Pasadena, one of which was available for test drives. I drove one, and liked it a lot. It can go 65 miles an hour and travels 110 miles before the battery needs to be re-charged. Think is an involved story. Willums, a repeat entrepreneur, bought the assets of the company out of bankruptcy from an investor group that in turn had bought them from Ford (F), which had sunk $150 million into developing Think before abandoning the project.

Today, the company is sprinkling a handful of cars around Europe. Then it will see if it can crack the California market. Rockport Capital partner Wilber James, who sported the only handlebar mustache at the conference, got into Think Global a couple years ago. He holds his own with Ray Lane, the ex-Oracle executive who is staking his investing career on a big play in electric cars. Other than Think, Lane has invested Kleiner’s money in Fisker Automotive (currently involved in a “ridiculous” suit — Lane’s words — with Tesla Motors, which says Fisker founder Henrik Fisker stole their ideas) and a third company he won’t identify.

As far as the U.S. is concerned, Think is more show-and-tell than anything. The cars won’t hit the road until 2009 at the earliest, and the partners haven’t worked out pricing, who their electric-utility partners are going to be (utilities love the idea of electric cars) or even where the vehicles will be manufactured. Having said that, the car is innovative. Think plans to sell the car but lease the battery on the thinking that battery costs will equate more in the buyer’s mind to gasoline prices. I’m in the target market: urban dwellers with short commutes who aren’t hung up on luxury trappings. I’d love to have one. Hurry up guys!

2. “Clean” coal. Before lunch on Monday I hosted a roundtable that asked if clean coal is an oxymoron. It was easily the most intense and enjoyable event of the conference for me. I’ll boil down the argument into two camps. Camp one: the coal industry, led by David Crane, CEO of the coal-powered utility NRG (NRG) and John Lavelle, president of General Electric’s (GE) business that sells equipment to coal plants to trap and “gassify” their carbon dioxide emissions. Camp two: mainstream environmental groups who want to encourage industry to do the right thing, led by David Hawkins of NRDC and Fred Krupp of EDF. Bitterly opposed to them were Mike Brune of the Rainforest Action Network, David Roberts of Grist.org (who had a ton to say about the conference at the Gristmill blog) and, though he didn’t overtly say he was against clean coal, Saul Griffith of Makani Power, a super-interesting MacArthur “genius” and entrepreneur.

Proponents of clean coal argue that coal is here to stay, that the Chinese and Indians are growing their coal capacity faster than the U.S. is, and that the best solution is to spend on technology to achieve the goal of clean coal. The opponents argue that even a dime spent on anything other than renewable fuels is misspent and furthermore that coal denudes mountaintops, gives people cancer and otherwise ruins life as we know it. Despite my caricatures of characterization, each side made compelling arguments. It was fascinating.

3. Wall Street and climate change. On this panel I had various executives from Bank of America (BAC), Goldman Sachs (GS), JP Morgan Chase (JPM), Lehman Bros. (LEH) (the banker with the best name in the biz: Theodore Roosevelt IV), and Ceres, a firm that advocates for socially responsible investing on behalf of oodles of dollars of pension-fund and endowment money. The gist of this panel was that Wall Street is incorporating global warming into its normal shtick, be that giving investment advice, attacking a lucrative market or encouraging its clients not to be polluters. There’s a bit of a feel-good patina to this, in my opinion. “Green” to the investment banks isn’t really that different from, say, steel or chemicals, in bygone eras. It is a PR opportunity, however, and it’s also a net positive that these influential firms are thinking about and doing the right thing, at least as they see it and as best as they can.

4. The skeptical environmentalist. Another highlight of the conference for me. I interviewed onstage Bjorn Lomborg, a Danish political scientist and statistician who is one of the leading voices against the mainstream approach to combating global warming. It’s way too tough to boil down Lomborg’s philosophy in a paragraph. But I’ll try. He thinks global warming is real and man-made, but he thinks it’s not nearly the greatest crisis facing humanity (world hunger, for example, would rank higher in his book), and he believes policies like the Kyoto protocol or proposed cap-and-trade schemes pending in the U.S. Congress are wastes of time and money. Lomborg has written two books on the subject, The Skeptical Environmentalist and Cool It.

In general, he’d rather see money invested in technology to combat global warming than regulation that enforces behavior that won’t greatly affect the problem. Lomborg is extremely controversial. Most environmentalists hate the guy. They think he’s a liar, that he fudges the facts and that he’s a toady of the “deniers,” people who believe global warming doesn’t exist. The write-up David Roberts did of my interview gives you a good sense of that perspective. I happen to think Lomborg makes a lot of sense, and that his perspective is totally worth considering. Even if you believe that global warming is an abject crisis, I simply reject the argument that it’s a bad idea to test your beliefs by listening to someone who disagrees or who is proposing a different solution. Check out an admittedly self-serving take by the noted entrepreneur Bill Gross, who was early, as he often is, to the green game.

5. Vinod Khosla. The famed venture capitalist was on his game for a 20-minute interview with me Tuesday morning. Khosla, who struck out from Kleiner Perkins to start his own firm, Khosla Ventures, also was one of the early Silicon Valleyites to get that green was going to be a big money-making opportunity. He’s built a portfolio of some 40 companies, one of which makes corn ethanol, a product currently derided by just about everyone (other than Midwestern farmers and Archer Daniels Midland (ADM) ) as doing nothing for the environment and driving up food prices in the process.

Khosla isn’t backing away from his support for all kinds of biofuels. He thinks biofuels are a distant fourth in the blame game for rising food prices, behind soaring demand, drought in Australia and rising fuel prices themselves. He pooh-poohs hybrid cars, calling Toyota’s (TM) Prius a good example of “greenwashing,” and said that while most of “clean coal” is bunk he is interested in next-generation coal sequestration technology. That’s the process of sticking the bad stuff into the ground, and to get a handle on its rating on the controversy meter, think about the old debate on spent nuclear waste rods. David Roberts also liveblogged my interview. Todd Woody covered it too.

6. Investing on green. For my final panel, I brought up four people who are earning their livings trying to make money on the green craze, as opposed to people whose jobs are a mix of doing good and doing well. The four were Dave Edwards, the “clean tech” analyst at Morgan Stanley; Erik Straser, who has built an investing practice solely on the subject at Mohr Davidow; John Small, who spends about half his time on green investments for the giant hedge fund company GLG Partners (GLG); and Martin Whittaker, an investor with the private-equity fund MissionPoint Capital Partners.

A very short takeaway from this panel is that despite all the noise, this field is incredibly young. There aren’t that many public companies in which to invest. That’s why solar-panel makers like First Solar (FSLR) have been so volatile: 52-week range of $54 to $308; currently at $286. As Straser noted, green tech hasn’t yet had its “Netscape moment.” I’d love to have all four back on stage next year for a progress report.

Some other random comments from the conference. Microsoft (MSFT) has a chief environmental strategist now, and he happens to be a friend of mine, Rob Bernard, who has been with Mr. Softee for more than a decade. I did a video interview with Rob that explains what a software company’s environmental strategist does … The environmental crowd is a lot of fun. I loved going to a Fortune conference and seeing lots of people I didn’t know…The food at our conference was amazing!