This is one of the best iphone applications I've seen in a while. I love music and when I want to know the name of the artist who sings a song, I use Soundhound to search out that information.
This great app is faster than any other app I've seen at determining the name and singer of a song. A quick search at the Apple iTunes store and Soundhound has both a free version and a more advance paid version, available for the iPhone and iPad!
It easily links to iTunes so you can quickly purchase a song to keep on your mobile device. Well worth the money, this application kicks butt!