Mesa is an open-source implementation of the OpenGL specification - a system for rendering interactive 3D graphics.
A variety of device drivers allows Mesa to be used in many different environments ranging from software emulation to complete hardware acceleration for modern GPUs.
Mesa ties into several other open-source projects: the Direct Rendering Infrastructure and X.org to provide OpenGL support to users of X on Linux, FreeBSD...
preview:
http://www.mesa3d.org/
10/17/2008