Flash Flash Revolution
OK. I'm not playing it right now. But I've been playing Flash Flash Revolution almost daily for a month or so now, and I just can't stop. The game is a Flash version of the popular arcade game Dance Dance Revolution in which players do dance steps on floorpads according to choreographed patterns demanded by the game and are scored based on rhythmic and stepping accuracy. In FFR you use your keyboard instead of your feet, so the coordination is different (fortunately for me), but some of what you do with your eyes and brain is the same, and it's a lot of fun. You have to register (free) to play, but it's definitely worth it.