NaNoWriMo is an Adventure! It is a completely mad-dash through 50,000 words in thirty days.
I have just completed–and won!–my third go at this.
2006 - I first signed up that year, but it was too heady for me and time too crunched. I watched it sail away, but that seems to be part of the process. It captures your imagination and you come back when you are ready.
2007 - I wrote a spontaneous novel that I continued writing and working on for more than two years. I learned to write a rollicking story by the seat of my pants and have been editing and polishing it ever since. I think it's done.
2008 - Still working on the 2007 novel.
2009 - My rebel year. I used the NaNoWriMo month to further a new WiP novel by more than 50,000 words.
2010 - I stretched out in a new genre with a complicated POV switchback structure. I anticipate 30,000-40,000 more words to completion of the first draft. This one was hard. I was uncomfortable. We'll see what becomes of it, but at the very least, I have grown as a writer and tried new things and made myself write those words everyday.
It is an awesome workout to write like this. And, after NaNoWriMo, it certainly makes going back to a regular writing schedule look very sane.