Pandora.com and Jamendo.com (free legal music)
I've been using http://www.pandora.com and http://www.jamendo.com (jamendo's homepage is messed up go to http://www.jamendo.com/en/albums/ ) and I love both sites.
Pandora is a music discovery site that streams you new music based on how you've rated what you've told it to play. it also provides info on the song band and album. they even have a facebook addon (which my friends and i love)
Jamendo is a site where artists o.k. with giving out their music for free can put it up on to be downloaded, heard and rated, all the music is gotten can torrented downloaded or streamed as either mp3 or OGG. they have 9000+ plus albums of many genres. Jamendo also has a plugin for the Gnome music player Rhythmbox (which is how i found it)
both sites are totally free and don't require that you join to use them.
while pandora has really annoying ads using the noscript extension for firefox will turn them off.