The most surprising lesson we have learned from simulating complex physical systems on computers is that complex behavior need not have complex roots. Indeed, tremendously interesting and beguilingly complex behavior can emerge from collections of extremely simple components. -- Chris Langton
In these systems, agents residing on one scale start producing behavior that lies one scale above them: ants create colonies; urbanites create neighborhoods; simple pattern-recognition software learns how to recommend new books. The movement from low-level rules to higher-level sophistication is what we call emergence. -- Steven Johnson
In A Nutshell: Living, self-organizing systems develop from the bottom up, within the context of their environment.
Exploring Emergence - a fun site that uses interactive applets to explore examples of emergent behavior.
Boids - a java applet demonstrating the pioneering program of the same name (from 1986), which was one of the first models of emergent complex behavior.
Emergence - A short video by PBS and Nova that explains emergence.
Complexity and Self Organization - provides an introduction to the basic concepts in the field of complexity science. (pdf)
How It Can Apply In Our World
Command and (Out of) Control: The Military Implications of Complexity Theory - a presentation at a 2-day symposium sponsored by The National Defense University and the RAND Corporation in November 1996.
Complexity and Chaos in Nursing - a journal focused on using the paradigms of chaos and complexity to develop new concepts and theories for the field of nursing.