Open Source Solid Modeling CAD
Vivid3D is a C++ IDE/3D engine, with python scripting.
LDraw™ editor for LEGO® style digital building instructions.
Design your own pottery for 3D printing in full color
Gimpel3D - 2D/3D Stereo Conversion Editor
3D world editor for game development
Pear3DEngine is a modern and modular 3D development framework
true 3D Labyrinths - generating, rendering, exploring, building