A life-long fan of games
of all sorts, one of the deciding factors that brought Holland to UMich
was the fact that it was Pac 10
and he couldn't stand to be at a school with a lousy football team
Along with genetic algorithms, his most famous concept is that of complex adaptive systems, or cass, which he describes clearly and succinctly in his slender tome, Hidden Order. This book also touches on how his work interfaces nicely with both John Von Neumann's game theory and John Maynard Smith's notion of evolutionarily stable strategies.
A nice overview of his work, and that of the Santa Fe group may be found in the M. Mitchell Walkdrop book Complexity: the Science Emerging at the Edge of Order and Chaos.