Veusz is a GUI scientific plotting and graphing package. It is designed to produce publication-ready Postscript or PDF output. SVG, EMF and bitmap formats export are also supported. The program runs under Unix/Linux, Windows or Mac OS X, and binaries are provided. Data can be read from text, CSV or FITS files, and data can be manipulated or examined from within the application.
MayaVi is a free, easy to use scientific data visualizer. It is written in Python and uses the amazing Visualization Toolkit (VTK) for the graphics. It provides a GUI written using Tkinter. MayaVi is free and distributed under the conditions of the BSD license. It is also cross platform and should run on any platform where both Python and VTK are available (which is almost any *nix, Mac OSX or Windows).