ipod-itunes

iPod.iTunes evaluates the source for content (songs, videos, podcasts and/or playlists) and only adds missing content seamlessly to the target, without duplicates, saving your time.
Unlike iTunes' own one-way mirror-synchronization iPod.iTunes leaves your content intact, nothing will be deleted during synchronizations (add-synchronization).
iPod.iTunes can also transfer song dependent meta data like "My Rating", "Last Played", "Play Count", album artwork, etc...