Just saw the link to this on Penny Arcade, Harmonix are starting to roll out their answer to Guitar Hero's song creator, and they're definitely raising the bar.

The Rock Band Network is a revolutionary system that will allow bands, studios and record labels to create and sell playable game content from their master recordings using the same professional tools used by our developers. Use our tools to author playable tracks. Upload and submit your tracks for review by the Rock Band Creators community. Approved tracks become available in the Rock Band Store and on the Xbox LIVE Marketplace, and you get a cut of every purchase.

Theres a website up for it, which doesn't have a lot of info yet, but does have a video that gives a bit of a taste of what the Rock Band Network is and how the whole system is going to work. Pretty awesome stuff!

http://creators.rockband.com/ or the article referred to on PA.

Sounds neat.