Ajaxna is a javascript API enabling 3D games for the web, without using plugins. This programming framework targets Visual Studio 2008, follows an XNA inspired API, is implemented as a C# ASP.NET control and is built around dynamic client class (lazy) loading and intellisense.

3D graphics engine, targetting Silverlight, Windows Phone 7, Xna and OpenGL.

Entropy3D is a 3D Game Engine aiming for simplicity and ease of use.

Goblin XNA is a platform for research on 3D user interfaces, including mobile augmented reality and virtual reality, with an emphasis on games. It is written in C# and based on Microsoft XNA Game Studio 3.1 (up to Goblin XNA v3.6) and 4.0 (after Goblin XNA v4.0).

Jad is a 3D Game Engine completely built in C# + MDX. It offers great graphic capabilities using the power of shaders 2.0, plus it´s own AI library and integrated physics thanks to the Newton Physics Library.

The Trench is a XNA based game, based on modern infantry combat.

Xngine is a casual game engine made of XNA component, each component can be reused to as it si to build different application like 3D rendering view, but all toghether they make a RAD for casula game with XNA. Xngine is a 3D egine with some facilities for statisc adn level managemtn, all the engineis a pure C# project.