I have been waiting for the "next" web 3D virtual world tool following Atmosphere & Second Life.
http://people.envision.purdue.edu/~tjrogers/

Though camera/geometry precision and self-building is not yet present, I had fun for a couple hours making my first room (based on my Media Display Prism Framework) and streaming six of my research-related youtube videos onto a virtual lively TV. Fun! Just in time to integrate my son Tristan's first avatar into the mix.

The computer I used to capture assets for this video didn't have the chutzpah to capture at very high frame rates, but I did the best I could given the available resources. There are a few video overlays to make up for some ugly spots, but overall, this exercise proved to demonstrate conceptual components of the MDP framework. I am even considering looking into using Lively as a platform for my dissertation--but that needs a lot of looking into. (less info)