I've been very remiss in not pointing out the many excellent pieces on Moneyball published over the last couple of months. For a good reference, go to Mariners Musings and scroll down to the appropriate right-hand list of links. The lucky Mariners fan has also transcribed interviews with Michael Lewis and Billy Beane conducted by Will Carroll on Baseball Prospectus Radio.
Also check out this interview with Michael Lewis on Baseball Primer, which contains some nuggets I hadn't seen elsewhere. Slate had a fabulous discussion between Rob Neyer and James Suroweicki about the book; the three parts are here, here and here. They also featured a great interview of Bill James by Suroweicki. Finally, check out this article by Matt Welch.
UPDATE: I forgot a few things - most notably, this recent review in the Weekly Standard:

[Lewis'] most recent book, "Moneyball," is the best business book Lewis has written. It may be the best business book anyone has written.
(Emphasis in original.)

And I had meant to discuss this excerpt from the book about fact-checkers, but Matt Welch beat me to it. Daniel Okrent, a writer for Sports Illustrated, had read the first Bill James Baseball Abstract:

“I was absolutely dumbstruck,” he said. “I couldn’t believe that a) this guy existed and b) that he hadn’t been discovered.”
Okrent flew to Lawrence [Kansas] to make sure James indeed existed, then wrote a piece about him for Sports Illustrated. It was killed: James’ arrival on the national sporting scene was delayed by a year, after the Sports Illustrated fact-checker spiked the piece. “She went through it line by line,” recalled Okrent, “saying ‘everyone knows this isn’t true. Everyone knows that Nolan Ryan attracted a bigger crowd when he pitched, that Gene Tenace was a bad hitter, that…’” Conventional opinions about baseball players and baseball strategies had acquired the authority of fact, and the Sports Illustrated fact-checking department was not going to let evidence to the contrary see print. The following year an editor who had been unable to shake Okrent’s piece from his mind, asked Okrent to retry again. He did, and the piece was published, and Bill James was introduced to a wider audience. The year after that, 1982, a New York publisher, Ballantine Books, brought out the Baseball Abstract, and made it a national best-seller.
This story has additional resonance in light of the Jayson Blair scandals.