Spotify is basically a combination of iTunes and radio.  You can look up an album, song or artist and then listen to the entire playlist that pulls up.  It is legal and so far FREE (though my husband says that it is still in beta form, and the "free" might change after they see how well it markets.)  For the time being though, I have been enjoying listening to musical artists and soundtracks just like I would on our iTunes with very rare commercial breaks.. and did I mention FREE??  Obviously they don't play some of the more obscure musicians or albums, but I've been quite impressed with their extensive selection.  I think we've listened to every version of "The Wheels on the Bus" that are out there during the course of my son's obsession.