Second Life research data

Economic Statistics (official Second Life website)
http://secondlife.com/whatis/economy-data.php

Comparison of Virtual Worlds (Active Worlds, Second Life, There)
http://oz.slinked.net/compare.php

Second Life: The Educational Possibilities of a Massively Multiplayer Virtual World
http://www2.kumc.edu/netlearning/SLEDUCAUSESW2005/SLPresentationOutline.htm