Evolutionary Game Theory by Joergen Weibull. We've actually been doing a few weeks on that in this quarter's game theory course. It's kind of cool - we proved the fundamental theorem of natural selection (that under certain circumstances average population fitness increases) in one of our problem sets. There's some interesting work being done on the evolution of utility functions and these tools could be good for that.
Skint as usual, because I booked my flight home (21 July). And discovered that I actually have a month more in my apartment than I thought... which actually sucks because it means a month's more rent. Doh.