I think this web page has been around for awhile, but it is still cool nonetheless. Harmonix and MTV Games have a website that lets you request a song you really want to see in
Rock Band. It also lets you suggest a band or artist that they may not have considered yet. All you do is head over to the
Request a Song page at RockBand.com, enter in a song or artist and a small blurb on why it rocks. Obviously there is no guarantee that your suggestion would be used, but like anything else, unless you ask, you will never know.