These are spread out around the net and move from the fiction to the non-fiction side.
Medium is an online community where people write about everything. From thoughtful essays about our changing world, to fiction, and everything in between.
NAtional NOvel WRIting MOnth occurs every November and for 30 days participants try to write 1,667 words a day. The goal is to get 50,000 by midnight on November 30th.
I've participated a few times, successful once.