I’m not exactly sure how it is that I’ve never heard of this before. Maybe I have, but it didn’t make enough impression on me back then. MusicBrainz provides audio file metadata (somewhat like the CDDB), but it does it based on an acoustic fingerprint. The artist/song name/album name tags on my music tend to be of good quality already, but it wouldn’t hurt to do a run-through and cleanup. For the Mac, there’s IEatBrainz to clean up your iTunes library.
All this talk of brains is making me hungry. 🙂