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...
The Python Computer Graphics Kit is a collection of Python modules that contain the basic types and functions to be able to create 3D computer graphics images (focusing on Pixar's RenderMan interface).
Maxwell Render for Blender
B-Maxwell add-on offers seamless integration with Maxwell Render and Blender
KlayGE is an open source, cross-platform game engine with plugin-based architecture. It provides a framework to make game development, testing, porting as simple as possible.
This software can be used for relief and normal maps calculation by 3D sculptors and designers. Reliefer can be called from Blender by means of Python script. It's a GPU-based visual computing application so requres OpenGL 2 compitable video subsystem.
Renderer that uses new techniques for achieve maximum flexibility and precision while preserves necessary performance.
GMUVE (Graphical Multiuser Virtual Environment) is an engine/framework that lets large numbers of users interact in a 3D world. GMUVE is a peer to peer networked OpenGL application that can be used for MMPOG or 3D chat. It is available in Python and JAVA
"LiAR isn't a raytracer" is a cross platform, object-oriented and extendable raytracer written in C++ and Python.
The Oxonium 3D Engine is a small, fast, cross-platform 3D Engine built so that mortal men can understand the source.
Hyzenthlay, named after the Efrafan Doe from Watership Down rather than the plant, is a vector-based graphics rendering, manipulation and machinima program, distributed in Open Source fromat programmed using Python. This project is currently in plan...
PyGLSL is a GLSL wrapper for Python to access Vertex/Fragment Shaders on top of PyOpenGL - Requires pyrex and OpenGL>=2.0
QShed is a system designed for the graphics and animation industry. QShed utilizes the latest technologies to create a distributed network using a LAN and/or the Internet to render graphics.
RTT which stands for Ray Tracing Toolkit, aims to supply a high level interface to fast ray tracing in python.
The Scientific Visualization Artist Tools (SVAT) include converters from the Visualization Toolkit (VTK) to RenderMan Interface Bytestream (RIB) (ASCII and binary files supported), Blender to RenderMan, compilable RenderMan shaders and other utilities.
Skill is a Blender modelling/rendering documentation website, and also a program that teaches you how to use Blender techniques.
A library and many frontends written to achieve an unbiased renderer with many features and good performance.