using mediamonkey and using the Auto-Tag from Amazon feature. Usually does pretty good, but not 100% accurate. you'll most likely have to do it by hand.
WHen i transfer music to the player using creative mediasource, some music becomes labeled as "unknown" in the player, when i try to access it in the music library. Anyway you can fix that in a fast and simple matter other than going through them all and changing the names manually using mediasource?