Wondering if anyone else has noticed this... I realized a couple years ago that I tend to like bands that sound like Soundgarden but aren't Soundgarden (who of course I love too). So, I created a Pandora.com station and discovered all these great bands I'd never heard of - Acroma, Manmade God, Boy Hits Car, and Slave to the System being the best of them, I think.
I've started listening to it again lately, and yesterday I realized it had been a couple days now where every single band I heard I already knew. Soundgarden, Audioslave, Chevelle, Nirvana, even Korn at one point (which was when I switched it off) - there wasn't a single band that hadn't gotten a ton of radio play at some point in their career.
Last.fm is what I use for internet radio. It pulls out really obscure shit for me all of the time.