MediaMonkey is good software. It's an MP3 cataloguer / player that works well. Something like iTunes, only without all the creeping awfulness and with lots of useful features.
The main feature I use is the autotagger. It uses the filename and existing ID3 tags to look an album up on Amazon, then tags your MP3 files with cleaner names and cover art. There's an addon to get lyrics, too. The UI for this is great, with a clear view of and control over exactly what tags you modify. Solved my problem.
My only complaint is that MediaMonkey is not very good at actually playing MP3 files. It takes awhile to launch if it's not running already, the available skins are ugly, and it doesn't buffer enough off my NAS. But it's good enough though and you can always just use it to clean up your collection and play music via a more lightweight player.