Guitar Rising claims to be the next step up from the wildly popular (and super-fun) Guitar Hero series of games. It's PC based software that allows you to plug in your actual electric guitar to your computer and use a Guitar Hero-esque interface to measure your success in playing a range of different songs.
A big question is obviously - which songs. If you take a quick look at the song-list in this promo video, there's nothing that I've even remotely heard of but the website does mention that they are currently working on deals for song titles, so it could well just be the working list.
If it lives up to its promise, this could be a very exciting development in learning guitar. At the moment, its scheduled for release later in the year.