http://www.math.com/students/wonders/life/life.html
Conway’s game of life is always a fun thing to show kids learning about computer science.
Here is a nice, simple applet to play around with the Game of Life
http://www.ibiblio.org/lifepatterns/
Another good one:
http://vlab.infotech.monash.edu.au/simulations/cellular-automata/game-of-life/
If you really want to keep up with the world of GoL:
http://pentadecathlon.com/lifeNews/index.php
An epidemic simulator
http://vlab.infotech.monash.edu.au/simulations/cellular-automata/epidemic/
Here’s a simple ant colony simulator:
http://vlab.infotech.monash.edu.au/simulations/swarms/ant-sort/