Pybik is an interactive, graphical, single player puzzle about the cube invented by Ernő Rubik. Besides the cube, the program can handle towers and bricks (non-cubic puzzles). Pybik also has solvers, pretty patterns, and a collection of various moves. The cube can be manipulated with the mouse or keyboard. You can change the colors or images on the faces of the cube.
Tux Paint is a simple and entertaining drawing program geared towards young children. It has a simple interface, sound effects, and a cartoon character (Tux, the Linux penguin). Along with drawing brush strokes, lines and shapes, you can also enter text and place "rubber stamp" (or "sticker") images on the picture. Tux Paint is extensible, and could be useful in an educational environment (such as a grammar, elementary, or grade school). It's portable across numerous platforms, and runs well even on slower systems like the Pentium 133MHz.