Virtual Worlds

Introduction

Virtual worlds

Second Life
There
Active Worlds
Quest Atlantis

Other Projects

Open Metaverse: http://openmetaverse.org/wiki/OpenMetaverse
Multiverse: http://www.multiverse.net/
Croquet: http://www.opencroquet.org/index.php/Main_Page
Synthetic Worlds Initiative: http://swi.indiana.edu/