Carpet ghosts are those little indentations left behind when a piece of furniture has been resting in one place for a long time. If you're looking for a simple and efficient way to eliminate them, simply place ice cubes where the carpet has been crushed or matted. The fibers of the carpet will swell as they absorb the water. Once the ice cubes have melted, just blot the wet area with a dry towel, and vacuum the carpet to straighten out the fibers. Voila! Carpet ghosts are gone.
The Martha Stewart Show, February 2008