The R Project for Statistical Computing
This program is a comprehensive set of interactive software for statistical computing and science.
Builtin language is oriented programming object in front ends to several available interfaces, manuals, help pages full 2D and 3D rnews online newsletter, books and other publications, regular conferences, as well as high volume mailing lists.
It is also noted that 600 packages of addon is being offered for free.
Free of charge
Compatible on almost all OS