TweetMusic is a simple App that allows you to tweet details about the music that you are listening to. The App was earlier priced at $0.99, but the price of this useful App has been dropped, and it is now available for download via the App Store for free.
TweetMusic automatically detects the song that you are playing, creates an iTunes and YouTube link to the song, and tweets these details about the song on your Twitter account. You can also control playback using gestures, and search for music videos from within the App.
Get the App from here.