Vampire ecology
Cute article by Brian Thomas titled "Vampire Population Ecology," mathematically analyzing whether the town of Sunnydale can support a sizable vampire population over time (given various assumptions about vampire feeding patterns and Buffy's actions). There may be some very minor spoilers from early seasons, I'm not sure, but nothing that I would expect to surprise anyone who's ever seen the show. And you don't have to watch or like the show to appreciate the general idea. (Thanks for the pointer, Chaos!)