Open source music fingerprinting
LibOFA (Library Open Fingerprint Architecture) is an open-source audio fingerprint created and provided by MusicIP (http://www.musicip.com). It is available cross-platform (win32, OS X, nix), and available for anyone to use in their own digital music applications.
musicip-libofa - Project Hosting on Google Code
See also: lastmatch.py -command that identifies mp3s