PyFreeDBTag is a console program which uses information from the FreeDB database to (re)write metadata on digital audio files (MP3 and Vorbis, for now). It supports information editing, database searching, file renaming, and other bundles of niftiness.
libmetatag is designed to provide a C library to allow programs to read and write various forms of metadata in audio files, such as MP3, Ogg Vorbis, iTunes AAC, and WMA files, as well as utilizing MusicBrainz to query for CD audio metadata.