midomi

midomi is a music search engine with a difference - it is powered by your voice. You can sing, whistle or hum a tune and midomi should be able to recognise the track and artist. Once the track has been recognised you then have the opportunity to buy the track or album online.

You can have your songs stored and heard and rated by other users, find members who sound most similar to you and chat with people who have searched for the same music.
www.midomi.com