FlightGear Flight Simulator: free open-source multiplatform flight sim
An interactive viewer for three-dimensional chemical structures.
Xj3D is an open-source Java codebase for the X3D Graphics standard.
Scanning Probe Microscopy Controller and Data Visualization Software
Rayshade raytracer
3D .NET engine for Windows, Linux, Mac
Imagin Raytracer is a multithreaded command line raytracer
Game engine supporting many 3D/2D formats and graphic effects
A simple web interface for Blender, for rendering animations..
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor