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.
SongGenie - SongGenie analyzes, identifies and repairs your mp3 tags and names.
iTunes Duplicate Song Manager - iTunes Duplicate Song Manager with Folder Watch removes iTunes duplicates in Windows and Mac OS X.
Song Sergeant - Song Sergeant intelligently identifies and removes duplicates, renames inconsistently named artists...
TuneUp - TuneUp makes your music fresh and clean!
Wondershare TidyMyMusic - Optimize your iTunes and local music library with just one click.