...go to the post office, or rip a couple of fingernails out with a pair of pliers.
Ah well, the latter, while probably less unpleasant, won't get any letters mailed.
UPDATE: Got stamps at Kroger and coming home I caught the mailman exiting the neighborhood. I flagged him down, affixed stamps to my letters, and passed them from my car to his. Mission accomplished without having to enter the post office. Go Team Me!