GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
Giac/Xcas - Free computer algebra system
GNU Octave - GNU Octave is a programming language for scientific computing.
Geometry Pad - Geometry Pad is a dynamic geometry application for iPad and Android tablets.
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
Dr. Geo - Dr. Geo, a software to design & manipulate interactive geometric sketches.