The article Down and Dirty from the New York Times, discusses the growing populatiry of earthen floors. (subscription required)
Early one Saturday morning in January, Kevin Rowell dumped a bucket of dark mud on the floor of his big south-facing bedroom. It landed with a plop, spreading out and merging with a blanket of wet earth that already extended across much of the room. On his knees, Mr. Rowell took a trowel to the pile, nudging it this way and that until the mud was roughly level and about an inch and a half deep.