One framework for creating powerful cross-platform games
Unity3D Client And C# Server Framework
Vivid3D is an open-source 3D engine with powerful 2D UI.
Modern 3D engine and IDE written using C# and C++.
Mad Vandal's FortressCraft Mod Source Code
C/C++ , PHP, PYTHON, 3D ENGINES, CHROME NATIVE CLIENT
3D .NET engine for Windows, Linux, Mac
XNA based game engine completely written in c#
Gives agents personality, moods, emotions and emotional attachments.
Open Source Virtual World and MMOG Development Platform
Investigo - DX9 Performance and Debugging Toolkit