Who said that web 2.0 stuff needs to be dry and boring and... and...?
See this: Pandora, created by the Music Genome Project. Pandora answers the question "Can you help me discover more music that I'll like?"
By entering a song or artiste directly on the web page, Pandora automatically creates a radio station filled with similar music. Let the station run and work away! It's free. Each added song to one station brings in approximately 100 similar songs, so if you want to adjust the kind of music on any given custom station (you can create up to 100 stations), add songs progressively. By giving a thumb up or thumbs down to any song being played, the selection will improve over time...