NodeBox for OpenGL is a free, cross-platform library for generating 2D animations with Python programming code. It is built on Pyglet and adopts the drawing API from NodeBox for Mac OS X (http://nodebox.net). It has built-in support for paths, layers, motion tweening, hardware-accelerated image effects, simple physics and interactivity. 

PWGL is a free cross-platform visual language based on Common Lisp, CLOS and OpenGL, specialized in computer aided composition and sound synthesis. It is programmed using the Lispworks programming environment.

Visvis is a pure Python library for visualization of 1D to 4D data in an object oriented way. Essentially, visvis is an object oriented layer of Python on top of OpenGl, thereby combining the power of OpenGl with the usability of Python. A Matlab-like interface in the form of a set of functions allows easy creation of objects (e.g. plot(), imshow(), volshow(), surf()).

happily self employed independent software vender,
but enjoy consulting work related to my open source projects.

Structure Synth is a cross-platform application for generating 3D structures by specifying a design grammar. Even simple systems may generate surprising and complex structures.