A few of the Metaplace folks have announced that their first virtual world has been released on MySpace in the form of an app called Metachat, which you can add to your Myspace account right now. In terms of virtual worlds, it's not much -- there's a chat room, obviously, and a little soccer ball kicking area, and some RSS integration in terms of stock quotes, some weather info, and even translation features.
But even better than what it is is the potential that something like this represents. Social networks are already dabbling in social games (and planning even more interaction between the two), so a virtual space like Metachat may be the first virtual world that most of its users enter. It's a far cry from some of the more mature virtual worlds like World of Warcraft and Second Life (not that those two are all that mature, actually), but spaces like Metachat are a big sign of the coming collision of social networking and virtual worlds.