Bastet ("bastard tetris") is an ncurses Tetris clone which is harder than every other tetris released. It is based on a heuristics engine which tries to detect which block you need or don't need, and then gives you the blocks that you don't need. For instance, if you usually play by leaving long "canyons" one square wide and then waiting for the long "I" block, you'll have to wait till eternity before you see it. The heuristics have been worked on for some time and are quite nasty.
Macdoku is a Sudoku generator, assistant and solver. Its features include the ability to display possibilities based on the three main sudoku constraints, as well as the ability to highlight solved and erroneous squares. It uses Bill DuPree's "Sudoku Solver in C" as its solving engine and qqwing for puzzle generation. It allows you to play and print your puzzles.
ColorSnatch is a board game built using the Lazarus libraries. Player 1 starts in the lower left corner, player 2 in the upper right. Each turn, players choose one color to add to their territory. Then, all adjacent tiles of that color are captured. The first player to capture 50% of the field wins. It can be played vs. an AI or another human. Internationalization is available. The game is also a demonstration of Lazarus's capabilities.