Unity3D Client And C# Server Framework
One framework for creating powerful cross-platform games
Mad Vandal's FortressCraft Mod Source Code
A first person multiplayer shooter example project in Unity
.NET based API for Stealth Client
Android, DOS, FirefoxOS, Linux, MacOS and Windows all in one..
My fork of Manic Digger
Open Source Virtual World and MMOG Development Platform
A FastDL Server for Counter Strike in C#
Investigo - DX9 Performance and Debugging Toolkit
Anarchy Online Server Emulator