Avogadro libraries provide 3D rendering, visualization, and analysis
Open Source Solid Modeling CAD
LDraw™ editor for LEGO® style digital building instructions.
Java3d scenegraph editor
Cross Platform Professional Procedural Terrain Generation & Texturing
Gimpel3D - 2D/3D Stereo Conversion Editor
Pear3DEngine is a modern and modular 3D development framework
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor