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