SLED - Second Life Educators Mail List: Recommended by colleagues who are already active SL Educators. I hear it's a very active discussion list. Good place to start learning and getting some ideas from those in the field who are actively using SL for various education purposes. NOTE: The signup page I'm linking to isn't just for signing up. It also has some links to more resources and sites.
SLED Blog (K-20 Education Using The Second Life World): "This blog is written by educators and for educators, for those who are seasoned Second Life veterans and for those just starting out, for those who are die-hards and those who are skeptics. All are welcome. We hope you’ll read, enjoy, and comment on what you see."