I usually don't give cheap plugs for internet services but this is a great exception. Many of you know by now of Pandora Radio but for those who don't here it is. It is a free music service that queries by musical genre and constantly plays different bands of that type of music.
For example, create a "new station" and type in desired group (for example Bach) and it will start off with a song from Bach then follow it up with a different composer/band from that same type of musical type. This is a great way to discover new groups you might like from the desired genre. You can make a lot of different "stations" to toggle through different types. Once in a while a commercial will pop-up, hence how Pandora makes their living through potential sales.