What it is
puddletag is a tag editor for Linux loosely based on the Windows program Mp3tag. Basically it uses a table layout so that all the tags you want to edit by hand are visible and easily editable. However, puddletag excels at automating repetitive task like extracting tag information from filenames, renaming files based on their tags by using patterns(that you define, not crappy, uneditable ones).

But wait, there's more...
There're functions, which can do things like replace text, trim, change the case of any tag, etc. Actions can automate repetitive tasks, and then theres importing music libraries (though only QuodLibet is supported for now), automatic retrieval of tags via musicbrainz and more, so fire it up and explore.

Supported formats include: id3v1, id3v2 (mp3), AAC (mp4, m4a, etc.), VorbisComments (ogg, flac) and APEv2 (ape).

Why it is
Everything else sucked for various reasons and Mp3tag was the only reason I kept an XP partition around.

How it's different
Besides being buggier than Mp3tag (to be addressed), puddletag does a lot of things differently.

What you need 
At least Python 2.5.
PyQt4 (4.5 or greater) for the GUI.
PyParsing (>1.4) takes care of the parsing...
Mutagen (> 1.17 recommended, 1.14 required), tags and...
ConfigObj takes care of saving settings.
python-musicbrainz2 for MusicBrainz support.

The following are recommended. 
The Python Imaging Library in order to edit/view FLAC cover art.
QuodLibet must be installed in order to edit a QuodLibet library.

For Debian-based distros, use the following to install the dependencies. sudo aptitude install python-qt4 python-pyparsing python-mutagen python-configobj python-musicbrainz2 python-imaging

How to get it
Download it from SourceForge or check it out using svn: 

svn co https://puddletag.svn.sourceforge.net/svnroot/puddletag puddletag

Install it by running "python setup.py install" (Do NOT install from svn!) as root in the unzipped directory. The puddletag menu item can then be found under the Multimedia Menu.

License
GPLv2, which you can find at www.gnu.org/licenses/gpl-2.0.html.

Updates
Swing by the website (http://puddletag.sourceforge.net) monthly for updates. 

Support
Visit the puddletag website (http://puddletag.sourceforge.net) for links to the forum and bug tracker.