I don’t really “get” Second Life, and I’m perfectly content in my ignorance. I do know, though, that some very good second language teachers have found it helpful and blogged about it.
A Movable Life is a new web application that allows you to explore Second Life just through your browser and without having to download anything. You just don’t have the 3D graphics.
If your feelings about Second Life are like mine, but you find yourself with a little extra time someday, it might be easy to check it out through this site.