Online Australia Virtual World (AWABA)  

AWABA is a virtual reality world that has been built especially for students. It is free and there are simple instructions. The word 'AWABA' is an Aboriginal word meaning flat or plain surface. AWABA is a space where you can experiment - you can build a house or a skyscraper in the sky, create furniture and modify the landscape. You can also meet and chat to people your own age. 

MiamiMOO - An educational MOO, where students and instructors collaborate to reconstruct historical sites and reenact the events which transpired there.