Saige almost made me cry, because I had not thought about pozole in a long time. Anyway, to the practically perfect writeup above I will just add that, in Mexico, the corn used for this dish is called "cacahuazintle" or "cacahuacintle", a specific variety of white corn with floury kernels.
In Mexico City you can buy the corn pre-cooked at most supermarkets. There are restaurants that serve only pozole, called (of course) "pozoleria". They will usualy have the white, red and green variety.