While Diablo 3 doesn't arrive, how about getting your Windows 7 in the mood while you wait for its launch?

Create custom content for The Elder Scrolls V: Skyrim game.
Utility that allows you to edit TXD files.
2D simulator that allows exploring different physical and chemical interactions.
Utility for installing mods in GTA V and GTA Vice City.
Modification for Quake III that impresses