[BarTopDancer]

I really like MusicBrainz. It's fairly simple and community edited (so you should be fairly familiar with what you are dealing with even though it's mostly music techies who use it. I use it to manage my 40+ gigs of music.

Personally I recommend taking them out of your various musical program libraries and keep them in a basic "My Music" type library on an external drive (or just on the drive dedicated to the music). You can run the music through the player when you want to hear it, make your playlists and keep them on the player, but the base music is stored on your hard drive and your library won't be seperated.