GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
Graph - Graph is an open source application used to draw mathematical graphs in a coordinate system.
Giac/Xcas - Free computer algebra system
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.
Geometry Pad - Geometry Pad is a dynamic geometry application for iPad and Android tablets.
Dr. Geo - Dr. Geo, a software to design & manipulate interactive geometric sketches.