As I come across websites that are good resources for writers, I’ll try and drop them in here so I can build a list for us all.
Here’s a couple to start with…
http://www.nanowrimo.org/ of course
http://www.paragraphplanet.com/ and their partner site http://www.writing-workout.com/
http://www.writingontherun.com/startgroup.html
There are also cool things to do