SuperSync is the best way to visually compare and merge multiple iTunes libraries. All your music, movies, and playlists can be moved to all the computers you keep music on.
Keep track of all your music across multiple computers -- Mac OS X, Windows, and iPod; Compare and merge any two music libraries; Move music, videos, and playlists from one iTunes library to another; Export all or a subset of your library as a well-organized directory of tracks; Find partial albums, duplicates, missing tracks, corrupt files, and other common music library problems; Intelligently import media from a hard drive, iPod, or network drive -- getting just the files you want and without duplicates; Easily move your music library from Windows to Mac, Mac to Windows, or any combination; Access your home music library from anywhere -- upload/download songs, movies, and playlists; Share a common library with multiple iTunes users on a network drive; Access your MP3's and playlists from your Tivo; Access your music from a Web browser; See and play music from your iPhone, iPad, or iPod.
What's new in this version:
Remove duplicate tracks and get all your iTunes libraries merged.