For Windows users who love to sing along, iTunes Lyrics Importer not only pulls the lyrics for your favorite songs but will makes update your iTunes-managed music collection.
Using Lyricwiki’s extensive database, you can generate a full catalog of lyrics to encourage your best sing-a-long impulse. Simple to use, the application will provide you with lyrics for your collection. From there on, any time you add new music or update, run iTunes Lyrics Importer to rescan your collection and update the new songs.
You can specify whether you want it to automatically update the lyrics, or ask for your approval and allow for edits.
iTunes Lyrics Importer is freeware, Windows only
I found this information on LifeHacker.com.