I really like Seeqpod which is a new music search engine with results delivered as “playable search results lists providing results from across the web. Audio and video results are played inside a slick music player.
There is also the option to “discover” related artists based on your current results ala recommendation engine, similar to Pandora, Last.fm or Yahoo.
This is a really great app, and developers will love it to because it has been launched with an api allowing you to retrieve recommendations, as well as search results.
Interestingly, SeeqPod clearly consider themselves outside the scope of royalty payments because they are not hosting the tracks, merely acting as a search engine directing you to content made available elsewhere. For anyone from the RIAA, it may provide a useful snooping tool on anyone illegally publishing music on the web, but in the meantime it’s definitely worth checking out.