Check out the very spiff'em site: http://rivertwine.com
We're looking for new members now, and it's a bang up team of talents if you're interested in co-writing and doing shared world fanstuff. (It's ElfQuest, but a rather grittier, more realism-based flavor... if you can picture such a thing in a world of spandex-leather and impossible hair...)
Even if you don't feel compelled to join, have fun exploring the site. I've got some artwork and writing up there that isn't anywhere else.