GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
Line Graph Maker - Create a line graph for free with easy to use tools and download the line graph as jpg or png file.
Giac/Xcas - Free computer algebra system
Desmos - A beautiful, innovative, and modern online graphing calculator.
Geometry Pad - Geometry Pad is a dynamic geometry application for iPad and Android tablets.
GeoGebra - GeoGebra is free and multi-platform dynamic mathematics software for learning and teaching.