Dupin Lite - Dupin Lite is your iTunes duplicates manager.
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.
iTunes Duplicate Song Manager - iTunes Duplicate Song Manager with Folder Watch removes iTunes duplicates in Windows and Mac OS X.
TuneUp - TuneUp makes your music fresh and clean!
MPFreaker - Imagine a program that automatically fills in the missing information in your music library...
SongGenie - SongGenie analyzes, identifies and repairs your mp3 tags and names.