There's a pretty interesting article in the July/August 2007 issue of Online regarding one library's experiment with Second Life, the virtual world. If you subscribe to the magazine, it's worth a look if for no other reason than to say, "Yes, I'm aware of Second Life."
Lori Bell, Kitty Pope, Tome Peters, and Barbara Galik. "Who's on Third in Second Life: From Library 2.0 to Library 3-D. " Online: The Leading Magazine for Information Professionals. July/August 2007, pp. 14-18.