Psychology and the nearest possible explanation would seem to be the thing (Although some biologist in England has a theory about morphic fields that could explain it).
Western medicine, the kind that militant skeptics adhere to, works because it treats the body as a machine, which, in a way, it is. Basic common sense is used, as in: if he pancreas controls the blood sugar level, and the patient has a problem with that level, he must have a problem with his pancreas.
Eastern medicine works more on a hiccup cure basis; someone tried it, and it worked, so they did it again and it became tradition. Acupuncture was most likely invented by a very bored man in ancient China, who, when pressed to explain why he was sticking needles into people, muttered something about that chi thing the Taoists were always going on about.
Why, in a western sense, does acupuncture work? Well, we won't know if we keep on mumbling "'s not real science" and keep walking away. For all we know, it ccould be a very good placebo, it could stimulate the nervous system a certain way, or it could be that there really are fields of energy that can be controlled with needles.
As for feng shui: it's psychology. No explanation needed.