www.nanowrimo.org is the official site. They're performing yearly maintenance at the moment.
November is national novel writing month, NaNoWriMo for short. The idea is to write 50,000 words within that month. I successfully completed the challenge in 2006 and ended up with a fantasy satire novel I'm quite proud of. This will be the second time I tackle the challenge.
You're not supposed to start the actual writing until November, but you can start planning in October; making notes, character templates, charting your plot, etc.
A few people actually write a salable novel this way. Many more achieve the satisfaction of getting their inner novel out on paper when they were unable to do so without the crazy deadline. There's a great book that goes along with it. No Plot, No Problem! Your library may have it. There's also a writing kit. November is a tough month for novelists because Thanksgiving can be so hectic. You folks that aren't participating in the holiday would have an edge in writing time.
Anyone want to belt out a novel next month?