Martin Szugat gives us an overview on which concepts of virtual worlds and Second Life we see in the 2d Web.
Avatars are now a common feature of communities and the social character of 3d worlds are also emulated by the web. Websites try to create a sense of immersion that is the major characteristic of VWs.
With applications like MS Photosynth you create virtual-world-like 3d models of real environments. Online shops try to create a 3d experience when shopping, like the Otto Shop.
The real time aspect of 3d environments play a role in live shopping environments like Woot or Gimmahot. There are also real time quiz formats like 'Wie weit wirst du gehen?'.