Midomi

This wizardly program can identify just about any radio song when you hold your iPhone to a speaker. You can also sing or hum a tune and Midomi will identify it. That comes in handy when you've got a riff stuck in your head but don't know where it's from. The service will point you to the iTunes store to buy the track, if you want, or show you related YouTube videos (like amateurs lip syncing to the song, or playing it on their banjo.) Shazam is another great app that also identifies songs after just 10 seconds or so.