Puddletag is an audio tag editor (primarily created for) GNU/Linux similar to Mp3tag. Unlike most taggers, it uses a spreadsheet-like layout so that all the tags you want to edit by hand are visible and easily editable.
The usual tag editor features are supported like extracting tag information from filenames, renaming files based on their tags by using patterns (that you define, not crappy, uneditable ones). More Info »
Then there're Functions, which can do things like replace text, trim, change the case of tags, etc. Actions can automate repetitive tasks. You can import your QuodLibet library, lookup tags using MusicBrainz, FreeDB or Amazon and more.