Matplotlib

Quoting from the Matplotlib website,

matplotlib is a python 2D plotting library which produces publication quality figures in a variety of hardcopy formats and interactive environments across platforms. matplotlib can be used in python scripts, the python and ipython shell (ala MATLAB^®* or Mathematica^®†), web application servers, and six graphical user interface toolkits.

It allows generation of publication ready plots and charts from a python script. Just started using this in one of my current projects and finding it satisfactory so far. The matplotlib figures can also be exported to a number of bitmap formats and vector formats like PDF. A definite advantage compared to MATLAB.

I'm using Ubuntu these days, to install Matplotlib in your Ubuntu box:

1. Ubuntu software centre,
or
2. Install it using apt

$ sudo apt-get install python-matplotlib