I see that most schools want 2 (one from a podiatrist and one from a professor/academic advisor). Is it appropriate to send in more than that? I can't really seem to find on any websites whether or not they'll take more or not.
Send 'em in! I sent them through my school (ie, sent them /to/ my school's grad school advisory department, and they sent copies everywhere) and sent the same letters to each school; some required less, but nobody is going to bother you about that.