Virtual Worlds (VWs) are one of my areas of research. They are immersive, 3d, avatar-based cyberspaces. They are similar to MMORPGs; however they differ in being less explciitly for some objective purpose and are more open-ended. They are deisgned to be platforms for interaction and creativity.
An article I published: http://firstmonday.org/htbin/cgiwrap/bin/ojs/index.php/fm/article/view/2957 Oct 31