Asymptote: The Vector Graphics Language
http://asymptote.sourceforge.net/

Asymptote is a powerful descriptive vector graphics language that provides a natural coordinate-based framework for technical drawing. Labels and equations are typeset with LaTeX, for high-quality PostScript output. A major advantage of Asymptote over other graphics packages is that it is a programming language, as opposed to just a graphics program. This has been added to World Wide Web Reference Subject Tracer™ Information Blog.