PSTricks

PSTricks is a set of macros that allow the inclusion of PostScript drawings directly inside TeX or LaTeX source code.

It was originally written by Timothy Van Zandt and has been maintained in recent years by Denis Girou, Sebastian Rahtz and Herbert Voss (de).

pstricks-add extends pst-plot enabling also polar graphs and allowing the use algebraic notation for plots instead of RPN.

pst-3dplot is used for creating 3D graphics like the following: multido provides basic loop functionality for programming graphs with repeating elements: pst-eucl is a beta extension for easy creation of geometrical drawings.

PSTricks is only fully compatible with TeX systems using PostScript intermediates, including but not limited to eTeX and others.

PSTricks example (scaled)
Plotting sin ( x ) with pst-plot
Hyperbolic paraboloid drawn using PSTricks package pst-3dplot
Plotting a graph while varying parameters with multido
Circumcircle of a triangle, illustrated with pst-eucl