I'm going to play a game of Lexicon, and you're invited. The original post detailing the game is here, but in essence this is how it works:
A group of players get together online to collaboratively create a dictionary for a completely fictional world. It's like a cross between Balderdash and storytelling. The players start with nothing but the title of the Lexicon, and then everyone submits the entries. As the entries grow, the world becomes better and better defined.
Check out the original article, and then take a look at the snazzy new website I built for it. I want to start playing the first game at the beginning of July, so please contact me (or leave a comment below) if you're interested. Also, please suggest titles and themes for the first game.