JamLegend

JamLegend is an online game in the vein of Guitar Hero and Rock Band. According to the JamLegend Web site:

Enjoy a potentially unlimited song list through a new platform allowing artists to promote their music in an engaging way. JamLegend features massive online multiplayer for real-time showdowns between thousands of players, as well as turn based competition for dueling with a friend. Robust social features, leaderboards, real-time notifications, and social network integration round out the features list. Best of all, it's free.

JamLegend seems to be positioning itself as not only an online game, but a place for artists to launch new songs that fans can then play. The site is currently in private beta, but you can sign up for an invite code and watch a trailer on the JamLegend.com Web site.