Gnuplot
From CFD-Wiki
Gnuplot is a freely available interactive plotting utility. It is capable of producing 2D and 3D plots and supports a number of different output formats, including:
- PostScript
- PNG
- SVG
- LaTeX
Gnuplot's primary interface is the command-line (though there are interfaces with other programs available), and it is one of the older free software programs still in development.