Qloud Plugin for iTunes is a very powerful plugin for iTunes.
Soundcrank 188.8.131.52 is an iTunes plug-in to get album artwork and lyrics.
Generates stunning graphic effects along with dynamic backgrounds.
A music/movie recommendation service in pair with a plug-in for media players.
A plug-in for Google Desktop Sidebar that can control both Winamp and iTunes.
iConcertCal is a free iTunes plug-in that monitors your music library.
iTunes sidebar for iTunes is a nifty application for iTunes.
Tenorshare Co., Ltd.
iTunes repair tool to fix all iTunes syncing problems and iTunes errors free.
iTunes Art Importer is still another feature-adding application for iTunes.
Binary Fortress Software
iTunes Sync is a great application for anyone who loves iTunes but not iPods.
iTSfv – iTunes Store file validator is an add-in for iTunes.
Nate DeSimone and Geoff Basore
iTunes Alarm Clock is an alarm clock that talks nice with iTunes.
Super PlaylistMaker 2.0 for iTunes - add 8 invaluable super playlists to iTunes.
LibZIP for iTunes - archive or transfer any part or all of your iTunes Music.
iTunes Toolkit brings you the features that Apple left out of iTunes.