QMentat helps you practice mental arithmetic. It uses arbitrary-length fixed point arithmetic, and can handle any size numbers, only limited by the size of your screen (and in the case of division with an integer result, the speed at which the number can be factored). It is also quite configurable, allowing you to tailor the questions to your needs.
libjmmcg is a basic, low-level library with pretensions to implementing features above and beyond (but not necessarily better than!) those implemented within the Standard C++ Library and the Boost Library. It features a library for multi-core or multi-chip SMP parallelism, a suite of hashing algorithms, functions for raising numbers to integer powers, a generic factory wrapper and a generic, multi-threaded, read-only cache (which uses PPD), arguably the world's worst sorting technique, trace output, exceptions that have the file, line, revision, function, and argument details, string utilities, logging, simple command line processing, and much more.
QSapecNG (Symbolic Analysis Program for Electric Circuits (New Generation)) is a Qt-based program for symbolic analysis of linear analog circuits. It consists of two independent parts, the SapecNG framework engine and the QSapecNG GUI. It was based on SapWin. Users can draw, solve, analyse, and manage analog circuits.