Xye is a puzzle game in which the objective is to get all the gems in each level. The mission is not as easy as it sounds: there are traps, monsters, and very hard puzzles everywhere. The player can interact with objects in the game in a lot of ways, and some of the objects can also interact with other objects.
YasSS (Yet another (simple|stupid) Sudoku Solver) is a Sudoku solver for the command line. It solves any Sudoku puzzle and generates Sudoku puzzles. It can calculate the number of solutions, print a difficulty rating, and generate a canonical form for a puzzle. It also provides a curses interface for playing Sudoku.
The Z-machine Preservation Project is a Java implementation of the Z-machine (Java version >= 5 is required) specification. This Z-code interpreter can be run either as a standalone application or as an applet within a Web browser. It runs Interactive Fiction created by Infocom as well as those compiled with Inform, and targets all existing story file versions. Features include saving the game state, multimedia support (graphics, sound effects, meta data), colored and styled text, undo, and timed input as well as support for different languages. Games in the Inform 7 release format are supported as well (Treaty of Babel specification).
Zaz is an arcade action puzzle game where the objective is to get rid of all incoming balls by rearranging their order. Currently it includes 20 different levels and two modes of gameplay. The engine allows for easy custom level creation with unlimited number of paths, different speeds, ball-sizes, and rules. A 3D accelerator is needed for decent gameplay.