The application I'm reviewing this week is available on both the Android market and the I-Phone market. Shazam is a simple to use app that listens to any song that is playing via radio,computer, other phone etc and gives you the name of the song, the artist, album, release date and a bunch of other goodies.
My personal experience with Shazam have been nothing short of awesome. It has never not been able to ID the song that I was listening to and it does it in such a quick time(depending on my current network). There has only been one issue with Shazam and that is you can only 'tag' or ID 5 songs a month for free. If you want to do more than that then you have to buy it for 5$.
Try it for free and post back your feelings/results.