G*Power
It says: G*Power is a tool to compute statistical power analyses for many different t tests, F tests, χ2 tests, z tests and some exact tests. G*Power can also be used to compute effect sizes and to display graphically the results of power analyses.
License: Free
GraphPad Prism
It says: GraphPad Prism combines scientific graphing, comprehensive curve fitting (nonlinear regression), understandable statistics, and data organization.
License: Commercial, free Trial
http://www.graphpad.com/scientific-software/prism/
GraphSketcher
For plotting and visualizing all kinds of data in many different ways.
License: Freeware, Source code available
http://www.omnigroup.com/blog/setting-omnigraphsketcher-free
IGOR Pro
It says: IGOR Pro is an extraordinarily powerful and extensible scientific graphing, data analysis, image processing and programming software tool for scientists and engineers.
License: Commercial, free Trial
Mathematica
Wikipedia: Mathematica is a computational software program used in many scientific, engineering, mathematical and computing fields, based on symbolic mathematics.
License: Commercial, free Trial
Maple
Symbolic algebra and data analysis.
License: Commercial, free Trial
MATLAB
Wikipedia: MATLAB (matrix laboratory) is a multi-paradigm numerical computing environment and fourth-generation programming language.
License: Commercial, free Trial
Octave
It says: GNU Octave is a high-level interpreted language, primarily intended for numerical computations. It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. It also provides extensive graphics capabilities for data visualization and manipulation.
License: Freeware
Orange
It says: Open source data visualization and analysis for novice and experts. Data mining through visual programming or Python scripting. Components for machine learning. Add-ons for bioinformatics and text mining. Packed with features for data analytics.
License: Freeware
Plot2
It says: A scientific 2D plotting program for OS X.
License: Freeware
R
It says: R is a free software environment for statistical computing and graphics.
License: Freeware
Scilab
It says: Open source software for numerical computation.
License: Freeware, Source code available