I was looking through the application store in iTunes and came across Midomi. It has been out for a while now and has gotten some great reviews, so I figured I would give it a try.
Basically, this program lets you hum, sing, type, or listen to audio. Based off of that recorded sample it will tell you the song. There have been many times when I have heard a song I really liked but had absolutely no idea what it was. With this application I am now easily able to "grab" a portion of a song and get the title.
I have hummed a few songs and it figured it out fairly fast. Some attempts at humming brought up multiple possible songs, but the one I hummed was definitely there. As for the grab feature, every song I have played on my computer here at work has been found and was correct.
This app may not have many uses, but it is definitely worth the download. Its free, so why not try it out?