Croquet

I've been using Second Life for more than a year and am now getting very curious about other virtual worlds.   Here is information on Croquet, which seems like a cool world!  The video is definitely worth watching.

Croquet is a powerful new open source software development environment for creating and deploying deeply collaborative multi-user online applications and metaverses on and across multiple operating systems and devices. Derived from Squeak, it features a peer-based network architecture that supports communication, collaboration, resource sharing, and synchronous computation between multiple users on multiple devices.