While we wait patiently to strum the hell out of these beauties leaked last week, PC owners the country over can enjoy the flaming greatness of Frets on Fire.
It's an open source game (which means it's free) based on Guitar Hero. Instead of a guitar controller however, you use F1-F5 as frets and the Enter key to strum. If you're not much into keyboards, no problem - Frets on Fire can use the Xbox 360 guitar controller.
I gave it a blast last night. I'm running Windows Vista Ultimate, and it picked up the Xbox 360 guitar without a problem. Frets on Fire treated it as a standard controller, so it was a simple matter of keybinding in-game.
I'll admit, it's not as smooth as Guitar Hero, and songs can go out of sync depending on the beefiness of your PC. It also makes use of OpenGL, so make sure your video card drivers are up-to-date. But, it does include a song editor and an import tool that can suck the songs off of the Guitar Hero I and Guitar Hero II discs, so you should have plenty to play.
Frets On Fire [Official website]