If you haven't already done so, check out Frets on Fire, an open source clone of the guitar hero franchise. Instead of a toy guitar, you are to hold your keyboard upside down and use the function keys as frets while "strumming" via the return key.
There are also a bunch of communities who add frets-on-fire files for a growing library of commercial songs as well.
A friend put me onto itsyourturn.com a few days ago. The concept is not unlike other turn-based on-line games available around the Internet. However, while other sites (that I am aware of) concentrate pretty much on one game, here, there is a whole host of games available for you to waste your time on, and you aren't restricted to just one game at a time. So, you can be playing 5 scrabble (known as Jamble for trademark reasons I suppose) games, 5 backgammon, 5 ... etc. all simultaneously.