Multiplayer mayhem! You run & jump around with other mice, trying to grab cheese and bring it back to the hole. One of the players takes the role of the shaman and gets to build ramps and add props to help (or not) the other mice grab the cheese. Chaos ensues of course, but it's an interesting experiment and I wonder if games like these will evolve and catch on.

UPDATE: alternate URL if it doesn't work (thanks Sander) and useful wiki with Shaman info (thanks Unforgiven)

I just rewatched Dr. Horrible's Sing-along Blog. The hilarious "Commentary: The Musical" that comes with it mentions that cast & crew were addicted to this game during the shoot.

It's a fun little time-waster that has you, the titular ninja, using two ropes to jump from one circle to the next. It's an iPhone game originally, so you just control it by clicking the mouse on the circles at the right time. To start the game, click the 'play' symbol in the top center.

Fun one-trick platformer. Your harpoon is a mobile platform of sorts. You can throw it at the wall and stand on it. You can even ride it in mid-air!