garith is a game similar in spirit to BSD's "arithmetic" or TuxMath. The game asks you to perform a simple arithmetic operation within a certain time frame. It improves your skills by stressing the operations you get more frequently wrong or that longer to answer. The statistics are saved/restored across games, so that each game is tuned for your current arithmetic abilities.
Project shyknight is a classic-style platforms game like Manic Miner and some others from early 80s. It has very nice and polished, colorful retro graphics, and simple but addictive gameplay. Eric is in love with a greedy girl named Martina. He must collect all the items she wants to make her happy.
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.
LinRadiant is a level (map) editor for FPS games that use id Software's engines (Quake 1/2/3). It is a derivative of NetRadiant with an improved build system. It is very easy to build, even for people with little experience in software development. It has built-in support for the following games: Darkplaces, Wolfenstein:ET, Nexuiz, OpenArena, Quake, Quake 2, Quake2world, Quake III Arena, Q3MIN, Tremulous, Warsow, and Xonotic. The package contains a lot of useful documentation (mapping tutorials, technical documents, etc.) that are automatically installed and can be accessed from within the editor.