Well, didn't I just learn something today – vexillology is the scholarly study of flags. I've made several posts in the past concerning my favorite flags, yet I was clearly in the dark about the vexillological arts. Indeed, the umbrella organization, the 'Fédération internationale des associations vexillologiques', has a fairly stunning flag of their own!
I discovered this newly minted member of my vocabulary after stumbling across the North American Vexillological Association's website via Jason Kottke. They have a wonderful guide to flag design — rules that could be easily adopted by logo designers of all stripes (heh heh). I especially love that they feature the flags of Amsterdam and New Mexico as first-class examples.