Ever listen to a song and forget who sings it? Ever listen to a song and want to buy it but have no idea who sings it? Shazam will tell you. If you have an iPhone, just load up Shazam via the iTunes store and run it. Here is a YouTube demo of me playing Stevie Ray Vaugn's Little Wing and Shazam listening to it and giving me the artist's name, song name and where I can buy the song. Amazing:

Here is the output of Shazam, after it finds the song:
Shazam in Action