I’ve been using Kid3 for my audio tagging needs for a long time. The in-built tagging functionality of Rhythmbox isn’t suitable for tagging multiple items. Then UbuntuGeek tells me about puddletag.
Puddletag is the best tagger I’ve seen. It’s got almost all the functionality you’ll need to manage your music collection. The options include downloading tag data from various online sources and renaming the file names. The app’s still in its beta and the deb installer can be downloaded here.