Pandora is a FREE online music source that plays music based on your individual tastes and moods. Simply enter a song or an artist (or several) and it creates a playlist that contains similar music.

The Twitter client that redefined Twitter clients is back, and it's even better. Rewritten from the ground up with a fast and powerful new core, Tweetie 2 offers the most polished mobile Twitter experience around.

This application blows me away. Hold your phone so that the mic can "hear" a song, and the app will tell you the artist and title. I think it also offers iTunes tagging.