Ceiling fans in winter

I always thought ceiling fans were mainly for summertime use, keeping areas cool to reduce or eliminate the need for air conditioners. I heard a tip on the radio last week, though, that makes perfect sense: During the summer, set ceiling fan blades to run counterclockwise (to create a cool breeze), but set them to run clockwise during the winter (to move warm air off the ceiling and down into the room). What a simple way to eliminate the problem of heat rising!