Graphing Calculator!

Gnuplot is a portable command-line driven interactive data and function plotting utility. It was originally intended as to allow scientists and students to visualize mathematical functions and data. It does this job pretty well, but has grown to support many non-interactive uses, including web scripting and integration as a plotting engine for third-party applications like Octave. Gnuplot supports many types of plots in either 2D and 3D. It can draw using lines, points, boxes, contours, vector fields, surfaces, and various associated text. It also supports various specialized plot types. »

Functy is a 3D graph drawing package. It allows Cartesian, spherical and parametric curve functions to be plotted and altered quickly and easily. This immediacy and the vivid results promote fun exploration of 3D function.

MathMod is a mathematical modeling software to visualize and animate implicit and parametric surfaces.