I remember an online VRML pseudo-MMO that pre-dated SecondLife and friends by quite some time in the late 90s. I think it was called CyberCities or something.
Fondly, I was amazed at its scope. Too much too early I guess. The only viable market at the time was high end businesses (I remember a famous demo of an in-browser car design vrmlet: colors, coating). But it was a niche.
I remember not just VRML, but noticing vwww.domain.com (or something similar) and thinking how it was going to be the future. Then I started using some random "3d" browser that allowed you to see webpages in a cube-like (compiz-like) environement. This was about 2001, which was the start to my interest in cgi and animation.
http://en.wikipedia.org/wiki/VRML