It's always fun to look up the song chords to your favorite tunes, especially if these songs happen to be ones you hear often on the radio. The Capo App for Mac computers and iPhone users is a great tool to have if you're interested in learning how to play various songs acoustically.
This app cleverly uses musical detection to figure out the various chord progressions in a song. All you have to do is hold your iPhone up to a song and let the Capo app track the melody. From there the app will tell you what songs were used to construct the song so you can play them yourself. This is a great app for guitarists learning how to play or looking to create their own songs.