Introducing the BitCoin Money Making Game.
Rules are simple: you place a bet, and then someone else pays the same amount of money that you used to place a bet. Then random one of you gets all the money.
Game is Jabber-based: you can start playing by contacting bot (bcmmg@bitcheese.net) via Jabber and sending "HELP".
Source can be downloaded here: http://gitorious.org/bcmmg/mainline