These can be a lot of fun, and they're cool!
Elementary Cellular Automata (http://www.emergentmind.com/elementary-cellular-automata#)
http://pmav.eu/stuff/javascript-game-of-life-v3.1.1/
http://en.wikipedia.org/wiki/Cellular_automaton
http://web.njit.edu/~matveev/Javascript/jjj.html - predator/prey
http://cubes.io/ (3-d)
3d cellular automata:
https://www.youtube.com/watch?v=dQJ5aEsP6Fs
http://www.bitstorm.org/gameoflife/
http://www.frank-buss.de/automaton/golautomaton.html
http://www.math.umaine.edu/~hiebeler/java/CA/CellularAutomata.htmlĂ˝