Entagged is an Open-source audio file tagger which provides a convenient way of changing the value of audio file metadata fields, either manually, or automatically via the freedb database.
Entagged can also do a lot of organizational work. You can rename your files from their tag in any way you like, including complex directory structures, or generate playlists for selected files and folders. Furthermore, you can also tag the files from their filenames, this avoids copying all the information by hand.
Best of all, Entagged hides all the different format complexities, with one unique interface. You can work with mixed file formats, eg. you can tag a mixed album of wma, mp3, ogg, flac, mpc, ape and mp4 files without worrying!
Note: version 0.31 does not seem to launch, try downloading version 0.30 instead. this is a cross-platform java app, hence the listing as a universal binary.