I've been told it's not good for you to shower more than once a day. If you wash too much you kill off your natural bacterial flora, leaving you wide open for infections. I've also heard that it's even less good for women to shower too often, because too much humidity can cause, well, unpleasant side-effects in certain intimate areas.
Also, washing one's hair with shampoo every day is, apparently, both unnecessary and not good for the hair. I have a friend who only washes his hair once a week, and it's the most magnificent mop of brown curls I've ever seen. He's a hotty.