Woow this is great and yes it actually does work, well for me anyway!

A Query by Humming system allows the user to find a song by humming part of the tune. No musical training is needed.The idea is simple: you hum into the microphone. The computer records the hum and extracts certain features corresponding to the melody and rhythm characteristics, then it compares the features to the features of the songs in the database. Finally it returns a rank list of the songs or song segments most similar to the humming.

A Query by Humming site