Muzzy - it’s a tiny and gorgeous iTunes companion that lives on your menu bar. For Mac OSX, its free!
Tune Sweeper - Show duplicates in your Music library. Automatically select which duplicates to keep and delete based on your preferences. Remove duplicates with one-click from your iTunes or Music app library.
Skip Tunes - Control iTunes, Spotify, or Rdio from your Mac's menubar
TuneUp - TuneUp makes your music fresh and clean!
Plaaying - Share, control, and keep on Plaaying music on your Mac.
SongGenie - SongGenie analyzes, identifies and repairs your mp3 tags and names.