Crystal Space is an Open Source 3D SDK for Unix, Windows, and MacOS/X. It renders with OpenGL and features GLSL shaders, CG shaders, deferred rendering, dynamic shadows, bullet based physics library, terrain engine, skeleton based animation meshes, exporter for Blender, portals, etc...
IMPFarm is a renderfarm for the POV-Ray raytracer. All communication is via http with XML documents. Servers and clients are cross platform. Management and reporting is done using web pages.
Exipnos is an Open Source, network based 3D virtual reality platform. The platform is intended mainly (but not exclusively) for eLearning applications. Role Player or Adventure Games might as well be developed and hosted on Exipnos.
Lamia or Lamia Engine is the modern generation free distributable and open source game engine for creating computer games for several prevailing software platforms and very maybe hardware platforms either.
The Open Descent Foundation (ODF) is a community for developers, who want to help to create open source programs, tools, etc. for the famous games Descent1, -2 or -3. Everyone can join the ODF if he accepts the idea of writing open source programs.
PerlGo: the classic board game of Go, featuring a Pov-Ray rendered game board and animation capabilities as well as SGF-import and autoplay.
To provide users with a customized rendering pipeline, right down to how the bounding code bounds. TRRT is about providing the rendering pipeline you want and need, whether you render at a professional or hobbyist level. Will be RenderMan compliant.
spyGLass is an OpenGL call tracer and debugger. It goes a step further than simply using ltrace because it knows what the arguments to the various gl* calls are, and it also knows about OpenGL's error flag.
vuVolume is a framework for volume rendering algorithms in C++. When creating a new rendering method in vuVolume it is possible to just concentrate on the actual algorithm and let the framework take care of the more administrative tasks.