BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
The Bubbling Load Monitor (or "Bubblemon" for short) is a system load monitor for the GNOME panel. It looks like a vial containing water. The water level indicates how much (electronic) memory is in use. The color of the liquid indicates how much swap space is used. The amount of bubbles reflects the system CPU load. A message in a bottle indicates there is unread mail. A reed-like graph shows I/O load. On multi-core systems the CPU with the highest load will bubble in the middle, and the others on the sides, so it's possible to see how well load gets distributed between CPUs.
C-XSC 2.0 is a C++ class library for eXtended Scientific Computing. It provides real, complex, interval, complex-interval, and multi-precision data types. There are also vector and matrix classes corresponding to these scalar types. The interval data types are very useful for verified numerical computations.
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.
Calc is arbitrary precision arithmetic system that uses a C-like language. It's useful as a calculator, an algorithm prototype, and as a mathematical research tool. More importantly, calc provides a machine-independent means of computation. Calc comes with a rich set of builtin mathematical and programmatic functions.
CCMATH is a mathematics library, coded in C, that contains functions for linear algebra, numerical integration, geometry and trigonometry, curve fitting, roots and optimization, Fourier analysis, simulation generation, statistics, special functions, sorts and searches, time series models, complex arithmetic, and high precision computations.
ChemApp is a programming tool from the area of computational thermochemistry. It is a library consisting of a rich set of subroutines, based on the thermodynamic phase equilibrium calculation module of ChemSage. It permits the calculation of complex, multicomponent, multiphase chemical equilibria and their associated energy balances. ChemApp is available as object code for a wide range of platforms and as a shared library/DLL. ChemApp "light" is the free version of ChemApp, and although it is restricted in two ways compared to the regular version, it gives you almost the same functionality.