Mac OS X
PlottingMy favorite plotting software has become matplotlib. It is inspired by MATLAB's plottng interface which is pretty powerful. It has two advantages though: it is free and it integrates into Python. Download it here: matplotlib download. Mac OS X users want the appropriate .dmg file and want to install the latest Python version as well (see above). They probably also want to install Aquamacs (see above).
Screenshots of Matplotlib
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