Carlos Gershenson, a friend of mine, has developed a suite of games with NetLogo for entertainment at parties. The games have to do with patterns that emerge as a result of the iterative application of  very simple rules by humans or other mobile agents.

Individuals are provided with a single, simple rule at the outset. The outcomes are sometimes independent of the initial conditions and sometimes sensitive to them, but nobody can anticipate them  (except perhaps Carlos and other complexity researchers).Some of the rules are as follows:
- “Approach one”: Each player chooses another player and approaches them one step at a time.  [ Some people ended up in the center of the room while others were  grouped in clusters.]
- “Retreat from one”: Each player chooses another player and then runs away from them. [Everybody ended up on the periphery of the room.]
- “Step between two”: Each player chooses two players, and tries to step  between them. [I had no idea what would happen. As it turned out, everybody ended up in a single tight cluster in the center of the room.]If different rules are issued to different individuals, interesting patterns emerge.

Recently, the New York Times  published an interesting article entitled “From Ants to People, an Instinct to Swarm” with graphs of ants that strikingly resemble  Carlos’ simulations.

As the article points out, people in the U.S. spend 3.7 billion hours a year in congested traffic, but you will never see ants stuck in gridlock. Carlos has himself  worked on improving traffic lights using auto-organization techniques. He recently earned his PhD with a thesis on the subject. Titled 
Design and Control of Self-organizing Systems, it has been published online as as ebook under a CopyLeft licence. It is an enjoyable work.References:
Gershenson, Carlos. Design and Control of Self-organizing Systems. CopIt ArXives, Mexico, 2007. TS0002ENFrom Ants to People, an Instinct to Swarm. New York Times, 2007.

Carlos Gershenson’s suite of games in NetLogo.