This Java applet was created by Curran Kelleher, a student at UMass Lowell and NECSI. It demonstrates the incredibly wide range of collective behaviors that can emerge from relatively simple rules of interaction.
Use the sliders in the pop-up window to vary several key parameters and see what kinds of behaviors and patterns result.
This is a different and very cool applet demonstrating emergence by varying physical parameters.
Emergent Behavior Applet