My favorite post-apocalyptic future.
Gordon Krantz, wandering minstrel, running from bandits, stumbles on the body of a postman, complete with his last bags of mail. He initially takes the mail merely as a way to gain entry to the few remaining guarded communities, to trade mail for food, but he's a dreamer and he's already aware that rebuilding civilization requires powerful symbols for people to believe in, and it occurs to him that the Postal Service - both mundane and powerful in pre-war civilization - is such a symbol. From there, in every community he passes, he establishes a postmaster, and links back to the communities he's already encountered.
It's a heartwarming story about the power of dreams, symbols, and our need to be part of society. In Brin's worldview, patriotism is not
the last refuge of scoundrels.