Have you seen http://chapterer.com ?
We are currently accepting submissions for Chapter One!
It's a brand new website designed to simplify collaborative writing. 3 projects a year, each is genre based.
Once a premise has been voted for, everybody is free to submit a chapter for chapter one. We shortlist them, and the community votes for the one they wish to make it to the final book! (which will be published!). The same happens for every chapter so you get the idea.
It's new, it's friendly, we aren't looking for stuffy pretentious writers but fresh and friendly folks with big imaginations.
Even if it's not your thing...you can submit short stories and poetry too!
Please check it out guys and girls, we need you.