Second Life is a 3D virtual world created by Linden Lab and is rising in popularity
There is only a small chance you haven't heard about it yet.
The applications of virtual worlds are many, like marketing, shared collaboration, connecting with your clients and so on.
COM.lounge is active in virtual worlds since 2006 (esp. Second Life) and is also part of the Architecture Working Group which aims to create an open, standardized protocol for interconnecting virtual worlds. This is called the Open Grid protocol and COM.lounge has just launched syntronik.de, the first native Agent Domain based on this protocol.
COM.lounge also aims to bridge the gap between the web and virtual worlds by bringing technologies such as Plone/Zope and Second Life together.