There are two twists to Lyrics Muse which makes it stand out. It's community based so anyone who registers can edit and improve the lyrics. The most cool differentiating factor however is that if you're a user of last.fm you will get your own personal interface to browse lyrics because Lyrics Muse tracks your listening.
In other words this makes it very easy to find the lyrics you need. It's the primary goal of Lyrics Muse to make it as easy as possible to find lyrics. Oh, and not plaster the site with irrelevant ads and popup crap.
If you sign up feel free to join the last.fm Lyrics Muse group to stay on top of news regarding the site.