MusicBrainz Picard lets you label and tag your music with the correct ID3 tags of artists, albums, etc. quickly and easily.
Picard is the next generation MusicBrainz tagging application. This new tagging concept is album oriented, as opposed to track/file oriented like the ClassicTagger was. Picard is written in Python, which is a cross-platform language, and makes use of cross-platform libraries - this allows the same code to run both on Windows, Linux and Mac OS X.