Helix Toolkit is a collection of 3D components for .NET
C# graphics library used for 3D modeling, built with OpenGL/OpenTK
Vivid Engine 2 is an open source 3D Engine coded using C# and C++.
3D .NET engine for Windows, Linux, Mac
XNA based game engine completely written in c#
Free 3D Photo Maker. Make 3D content yourself!
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor
A modern 3D App framework using OpenCL to render via raytracing