Reddit mentions of Swarm Intelligence (The Morgan Kaufmann Series in Evolutionary Computation)

The boids homepage has some good historical stuff. I believe there are a few swarm intelligence books out there like this one and then most modern stuff is going to be in conference papers and journals.

Note that the original boids followed very simple rules. You can get quite complex behavior with a few simple rules. The flip side is that it's extremely difficult to guarantee any kind of behavior in the control-theoretic sense with these kinds of multiple interacting systems. What we always did was have a good software simulation system where we could test out our new rules without the risk of crashing airplanes in real life. After many simulated runs, when we were convinced that the algorithms would behave well in most situations, we would port to hardware and test there.

Edit: Some folks are suggesting that the Kennedy book is more approachable.