only thing that comes to mind is pandora.com, but that's more of a playlist or something, you type in a band you like, and it plays similar music, or music it thinks you'd like judging by your predicition... i use to use it as a radio (because radio these days SUCKS

sorry, dunno exactly what you're looking for, but that's a good site nonetheless... still kinda what you're looking for, but somehow i get the feeling you're looking for something where you can type in a band, and it shows you a list and you can search for the music on it's own.