you(‘d) like to rock, preferably in an open source way? 
Then Frets on Fire is definitely something for you!
I was amazed by the polish-factor of this project! It all looks (and sounds!) quite nice, the tutorial is simply hilarious.
The inverted keyboard approach as a surrogate guitar works surprisingly well. I think in the 9 years that I own my trusty Mitsumi keyboard, I never jammed the keys as hard as today. 
Tip: FoF comes with only 3 songs, but you can import songs both from Guitar Hero I & II. Also check out this community site for some extra songs.
