Ok... this is totally un-fandom-related, but thanks to
irisgirl12000 I discovered
Last.fm.
I played around with
Pandora for a while, until they started blocking Canadian (or non-US IP addresses), and I was very excited to learn that I could use Last.fm... which is a similar concept.
I tend to just use radio for talk/news, so I tend to be a bit behind on new music (unless it's a band I'm already following), and now I can find new artists with styles similar to ones I already enjoy.