Programmeren: games

LOVE is a 2D game engine that enables easy cross-platform game development in the Lua programming language.
Ngd4Xna is a C# wrapper around the Newton Game Dynamics physics engine.
Ox Game Engine is an in-progress 3D XNA game engine. It is the reimplementation of the Buttermilk Game Engine in 3D.
RaycasterX is an MIT-licensed project geared towards the creation of a full raycasting engine for XNA.
Risen3D is an advanced Doom port by Graham Jackson based on Jaakko Keranen's Doomsday port.
The X-Engine is a game engine built around Microsoft's XNA project. It is designed to make implementation of many common and not so common features easy. It was built from the ground up in C# using XNA, and so is compatible with both Windows and Xbox 360. The X-Engine is built on the XNA Framework 3.0 CTP, and will be updated to XNA Framework 3.0 when it is released.
XNAnimation Library

Autodesk
Blender 3D (free open source)
DAZ
gCAD3D is a 3D CAD-CAM application that features an integrated 3D OpenGL viewer, a program interpreter for geometry and NC-commands in 3D, an integrated NC-processor, and a programming interface for user programs. It has support for importing Step files and support for both importing and exporting Iges, DXF, and VRML files.
K-3D is free-as-in-freedom 3D modeling and animation software
Lightfeather is a 3D engine for Linux, Mac OS X and Windows. It is designed to be easy to use but still take advantage of the features of modern graphics hardware.
Maxon
Plopp: 3D Painting tool
Swift 3D