Incredibox - Express your musicality, pump it up and chill
Narrow - Narrow helps you build a targeted audience and increase your influence on twitter.
Musicroamer - A visual Pandora for discovering new music
Follow3rs - Follow3rs enables you to add more followers to your Twitter account and become prominent in no time at all.
Music Walker - Explore and play (via YouTube) songs similar to a seed song.
Followerion - Followerion is the most trusted site regarding how to get more followers on twitter.