SkreemR is a brand new search engine that locates MP3 audio files on the web.
I had a sudden urge to listen to the Bee Gees and searching on the site gave me 1877 results. The innovative feature about this search engine is that you can straightaway listen to music straight from the results using their embedded media player.
You can also add SkreemR search to your Firefox search bar by downloading the Firefox Search Plug-In. They also have a new SkreenR add-on for Facebook users as well.
Read their FAQ for more info about the search engine.