C-Ship http://www.fourmilab.ch/cship/
A short overview of special relativity, filled with relativistic ray traced images. Explains relativistic effects using a theoretical spaceship.
Special Relativity http://www.motionmountain.net/C-2-CLSC.pdf
This is chapter two of Christoph Schiller's 1000 page walk through the whole of physics, from classical mechanics to relativity, electrodynamics, thermodynamics, quantum theory, nuclear physics and unification. 61 pages.