freedb: Audio CD database using GPL software.Gracenote: The CD Data Base (formely CDDB). Enabled CD players can query for playlists.Music Brainz: Project intended to be an OpenSource replacement for the existing system of looking up audio CDs on the Internet.Poqqo: A CD data server.The Free Track'Info'Xchange': Free data provider for the Deluxe CD Player that comes with Windows 2000.