Here's a cool and accessible article by David Austin on percolation:  [http://www.ams.org/samplings/feature-column/fcarc-percolation][1].  And if you do a quick Google search for "java percolation simulation" you will have access to quite a few nice in class demos.


  [1]: http://www.ams.org/samplings/feature-column/fcarc-percolation