GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
SciDaVis - SciDAVis is a free application for Scientific Data Analysis and Visualization.
GeoGebra - GeoGebra is free and multi-platform dynamic mathematics software for learning and teaching.
DPlot - DPlot graphing software lets scientists and engineers graph, plot, analyze, and manipulate data.
WinPython - The easiest way to run Python, Spyder with SciPy and friends out of the box on any Windows PC...
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.