Choose Your Own Adventure By Committee
I'm writing a story with help from friends and strangers on the internet. Every weekday, I'm posting 100-600 words and soliciting votes for what the main character should do next.
This is all happening on Google+, and I've been going for almost four weeks now. There's a bit more overview at the blog, which in theory should have weekly updates with links to that week's five installments. Actual participation should be on Google+, but the installments are public so we don't need to be friends or anything for anyone to participate.