Numerical and Symbolic Math Tool
Euler is a powerful numerical software and includes Maxima for seamless symbolic computations. Euler supports Windows or Linux via Wine. Download via the links on the project homepage.
If you want something like Matlab, Maple, Mathematica, Maxima, Octave, Scilab, Freemat, Axiom, Reduce, Mupad etc ... but to have more fun, just use Euler Math Toolbox.