Immersive+Education

SecondLife http://secondlife.com/

OpenSimulator http://opensimulator.org/wiki/Main_Page

OpenCobalt http://www.duke.edu/~julian/Cobalt/Home.html

Wonderland http://wl.igg.com/

ActiveWorlds http://www.activeworlds.com/

EduSim http://edusim3d.com/