Cactus is a general, modular, parallel environment for solving systems of partial differential equations. The code has been developed over many years by a large international collaboration of numerical relativity and computational science research groups and can be used to provide a portable platform for solving any system of partial differential equations.
distributed.net is a loosely knit group of computer users from all of the world that is taking up challenges requiring lots of computing power (most notably the RC5, DES, and OGR cracking contests). It is simple to participate in the challenges by downloading and running their client software (which uses idle CPU time to complete its tasks).
GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
Torch is a machine learning library written in C++ that works on most Unix/Linux platforms. It can be used to train MLPs, RBFs, HMMs, Gaussian Mixtures, Kmeans, Mixtures of experts, Parzen Windows, KNN, and can be easily extended so that you can add your own machine learning algorithms.
Calcoo is a scientific calculator designed to provide maximum usability. Its features bitmapped button labels and display digits to improve readability, no double-function buttons, undo/redo buttons, copy/paste interaction with the clipboard, both RPN and algebraic modes, two memory registers with displays, displays for Y, Z, and T registers, and tick marks to separate thousands. Calcoo is written in C using the GTK+ widget library (v.2.2+).
GLgraph is an interactive OpenGL based function grapher for Linux written in Perl. It visualizes any mathematical function in 1, 2, or 3 unkowns (x,z,t) in a 2D, 3D, or 4D wireframe or solid surface. It creates an animation after one time period. GLgraph has a command line interface to input a function, to specify the minimum and maximum plotting bound, and more. It can be interactively controlled with the keyboard.