ID Tunes for Mac

From Plum Amazing:

Once and for all clean up your MP3 song collection. ID Tunes goes thru your entire collection of MP3's using song fingerprint matching and enters all the correct tags (id3 tags are the fields that list the artist, title, track, genre, etc.). Now instead of 'Unknown' or 'Track 7' ID Tunes uses a variety of techniques to make sure that the correct Title is there, the correct Artist is there, etc. idTunes also cleans up your music collection by helping you find duplicate files and also by renaming files the way you want so that you can find music when you need to. ID Tunes performs its music recognition on songs by sampling and checking the sample against our web database of 3.5 million songs. idTunes will also search for lyrics and album art and add them to a song.