Gnu Octave

Open Source Computation Tool

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. Octave is normally used through its interactive command line interface, but it can also be used to write non-interactive programs. The Octave language is quite similar to Matlab so that most programs are easily portable.

KAlgebra

Open Source Calculator

KAlgebra is a calculator with symbolic and analysis features that lets you plot 2D and 3D functions as well as to easily calculate mathematical expressions. KAlgebra is a MathML-based graphic calculator, thought to bring to the user its power by solving expressions written in MathML or calculating converted common equations to MathML.

SpeedCrunch

Open source desktop calculator

A fast, high-precision and powerful desktop calculator.
Using SpeedCrunch you type the expression that you want to calculate and press Enter. You can paste the expression from the clipboard (that you copied from somewhere else) and you can copy the last calculation result to the clipboard using Ctrl+R.

Gephi - Graph Visualization

Gephi is a tool for people that have to explore and understand graphs. Like Photoshop but for data, the user interacts with the representation; manipulate the structures, shapes and colors to reveal hidden properties. The goal is to help data analysts to make hypothesis, intuitively discover patterns, and isolate structure singularities or faults during data sourcing. It is a complementary tool to traditional statistics, as visual thinking with interactive interfaces is now recognized to facilitate reasoning. This is software for Exploratory Data Analysis; a paradigm appeared in the Visual Analytics field of research.