OpenGeofiction is a map of an imaginary world, created by a community of worldbuilders. You can take part in this project too.
A collaborative writing tool built by a dream team. I’ve been using it for a while now and it’s very nice indeed.
Ficlets is back ...as Ficly. Take that, AOL: this site is just too good to roll over and die.
An interactive, collaborative timeline of the history and development of virtual worlds, open for anyone to edit.
Project Apeshirt is finally revealed and it's pretty darn cool — collaborative short fiction.