R
From Testiwiki
R is a programming language and software environment for statistical computing and graphics that is widely used for statistical and data analysis. It is free software that compiles and runs on a wide variety of UNIX platforms, Windows and MacOS. Off-the-shelf (and through using selected "packages") it is possible to use the software for Monte Carlo simulation, production of complicated graphics (over which the user has complete control) and a host of other applications.
