I was in one game where we held OOC chats and played games of 20 questions. You'd name a character, and every one would ask from their character's POVs a bunch of questions. It'd be all meta knowledge of course but people often took ideas from it to then use in IC threads where said information could actually be posed in an IC way.
A game I just joined offers something called a plottery, where they mods ask the players for plot suggestions on a regular basis, and then picks one at random to play out. It keeps everyone involved (or that's the idea anyway. The game hasn't started yet).
Another game I'm in has something called a 'Happenings Blotter' where people can submit stuff that's going on in town. Gossip, developments. business news, supernatural happenings, you name it. It hasn't really picked up as much as it could in a more active game, but it's a great idea.