What's NanoWrimo, you ask?
It stands for National Novel Writing Month. The goal is to write a 175 page (50,000 word) novel between November 1 and November 30.
Learn all about it at http://www.nanowrimo.org/.
I participated in 2005 and 2006, and though I didn't finish by the deadline during either year -- it sure kick-started my writing! I've decided to do it this year as a way to start working regularly on my third novel.
Give it a try, and good luck!
