Tombs of the Asciiroth is a puzzle/RPG/roguelike game you can either play in a Web browser or as an Adobe AIR application (available for Mac, Windows, and Linux). It is simple to play compared to most roguelikes, but the provided scenario should allow for some in depth game play. A map editor also exists to create new scenarios.
MUSoSu is a free software project for playing, solving, and generating Sudoku games. It is written in Java and emphasizes both solving Sudokus simulating methods used by hyman solvers and generating Sudoku problems that don't require trial and error methods to be solved. MUSoSu is partly themeable and platform independent.