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.
Ruzzle Solver PRO is an offline solver (aka cheater) for Ruzzle puzzles. It aims to be usable, fast, and easy to extend and improve for both users and developers thanks to a sensible and modular design. It allows you to add, replace, or update the dictionaries and the score tables, thus supporting an arbitrary number of languages.
Galois is a computer game of the "falling blocks" type, but with unique features. Unlike most other games of that type, it is not limited to blocks made of four two-dimensional, square bricks: you can choose among several different brick shapes, blocks composed of more or fewer bricks, and even between two- and three-dimensional games.
Gameclock is a fairly simple application designed to track the time spent thinking by the players during a chess game. Various clock engines are available (speed chess, fisher chess, board games, or hourglass). The graphical interface is keyboard-driven and is intended to be minimal and simple. The code is made to be extensible to other game types.