Check out
www.pandora.comIt works fairly decent especially if you start giving feedback.
Its a streaming internet radio that starts by asking you for a song/artist, then plays something close.
You tell it yes/no and it will refine the music to your tastes.
It helps to start with something very typical of what you want...It works by keywords referring to specific elements of the song (i.e. categorizing the bass line, ect...)
It can play some crap, but Ive found some groups I really really like and never heard of from it.
