Using CDDB to Fill ID3 Information in Existing MP3s?

masonbrown asks: "I've got about 2000 songs in my MP3 collection, using iTunes on the Mac. I'd love to fill in the empty ID3 tags such as Album Title, Date, etc. automatically from something like CDDB. Is there any way to automate this after the song is already in MP3 format (like going by Artist and Song Title)?"