MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
Maxima - Maxima is a fairly complete computer algebra system written in Lisp with an emphasis on symbolic computation.
Wolfram Mathematica - Mathematica has characterized the cutting edge in specialized processing—and gave the chief calculation environment to a large number of pioneers, instructors, understudies, and others around the globe.
GNU Octave - GNU Octave is a programming language for scientific computing.
SMath Studio - Tiny, powerful, free mathematical program with WYSIWYG editor and complete units of measurements support.
Sage Math - Sage is a free open-source mathematics software system licensed under the GPL.