Lots of people do this: put the pressure on themselves to write a book fast. After all, Jack Kerouac wrote On the Road in three weeks. (Kerouac's famous first draft in its scroll format is pictured here.)
First, there are the groups, that provide help and support.
1. NaNoWriMo stands for "National Novel Writing Month," with a website, forums, and a national following. Lots of books actually get written during this time period (in 2005, there were 59,000 participants and 9769 winners). You "win" NaNoWriMo by writing 50,000 words by midnight on November 30th. Every year, there are many winners. No awards are given; however, each winner gets an official "Winner" web icon and certificate. During the month, there are open forums, where lots of good advice is shared on writing, grammar, and other helpful topics.
2. BIW is similar to NaNoWriMo, but it is for those interested in writing a book in a week. The site is coordinated with a Yahoo Group, and on the first full week of the month, participants go for it. They are scheduled a year in advance. For 2006, the remaining three BIWs are: Oct 2 - 8; Nov 6 - 12; and Dec 4 - 10. The site is run by published authors, includes a chat room, and has a great list of helpful sites.
Second, there are online articles by writers who share their tips on fast writing.
3. Romance writer Elizabeth Rose wrote her first published novel (Eden's Garden) in two weeks, and provides the steps to do write a book in one month in two great posts: How to Write a Book in a Month, part one and part two.
4. Writer John Coyne offers How to Write A Novel in 100 Days or Less, with excellent, practical advice for each step along the way.
2011 Update: I may have found the book for me where you learn to outline and write your novel in 90 days, read about it here.