I've been using the Python based sympy (http://sympy.org/ http://sympy.org/) recently. While this isn't a replacement for Mathematica or even Maxima -- it's pre

I've been using the Python based sympy (http://sympy.org/ http://sympy.org/) recently. While this isn't a replacement for Mathematica or even Maxima -- it's pretty powerful. And being able to manipulate equations in python makes it easy to tie operations together. SAGE (http://www.sagemath.org/ http://www.sagemath.org/) is much more powerful but quite heavy in terms of systems resources.