It's a good idea, but I'm going to respectfully decline to do it myself. LEW had a "who's in the tavern?" thread for a while, but it turned out to be a ton of work to maintain and no one was interested in keeping up with it, so it became less and less accurate, and I don't think it's been right for a while now.
Maybe this would be a good application for wiki categories? If we had a "Looking for Adventure" category, that you remove yourself from when you've got an adventure, DMs could check that? Hmm, that might have problems though if unapproved characters get in it...