Graph - Graph is an open source application used to draw mathematical graphs in a coordinate system.
GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
Grapher - Put Grapher’s powerful graphing and data analysis features to the test and better understand your data. Learn about features and download a free trial.
GeoGebra CAS Calculator - Free online algebra calculator from GeoGebra: solve equations, expand and factor expressions, find derivatives and integrals
GNU Octave - GNU Octave is a programming language for scientific computing.
Graphmatica - Is a powerful, easy-to-use, equation plotter with numerical and calculus features: