Worldbuilder is a ning network called, "A fourth world media educational community." It is a rather new social network and one I feel has a lot of promise. Why? They do a very good job of advertising and sticking to their core philosophy, "Look, Listen, and Learn!"
This is a collaboration of educators dedicated to the educational use of social media. It really is a nice intriguing site.
As w/ most social networks, especially those created w/ ning, it is very user friendly and has a nice graphic interface.
I highly recommend giving Worldbuilder a look by clicking here.