Koch construction of fractals in PostScript: 0, 1, 2, 3, 4 (all for those that cannot handle PostScript in PDF).
Spirograph in gnuplot spiro.gp.
A few gnuplot scripts: cycloids (or here), shot, kepler, drop.
Riding on square wheels in a detail.
Falling spring, falling chain, Newton cradle, Gallileo cannon, Maxwell pendulum, Gömböc, balancing forks, ballistic pendulum, faster than free fall, moment of inertia, Foucault pendulum, energy conservation, momentum conservation.