Ever wanted to create a virtual world?

Now you can with OpenSim. Check this out: CLICK 

Features:

• Supports online, multi-user 3D environments as small as 1 simulator or as large as thousands of simulators.
• Supports 3D virtual spaces of variable size within one single instance.
• Supports multiple clients and protocols - access the same world at the same time via multiple protocols.
• Supports realtime Physics Simulation, with multiple engine options including ODE.
• Supports clients that create 3D content in real time.
• Supports inworld scripting using a number of different languages, including LSL/OSSL, C# and VB.NET
• Provides unlimited ability to customize virtual world applications through the use of scene plugin modules.