Lively by Google
It's not a secret anymore.
The Terms of Service are not very surprising and generally look similar to Secondlife TOS.
Two the most important differences:
1. Lively doesn't have currency.
2. The content in Lively is mostly generated by vendors working for Google and a small number of trusted testers.
So it looks more like clone of IMVU (combination of "chat with friends" in cartoonish 3D) than Secondlife or the Metaverse.