Inexpensive Cork Room Treatments

Had a happy discovery this week that inexpensive, egg-carton-waffled cork bath mats make great room treatments. They're 24" x 18" or 36" x 24", and the price of a couple of CDs. My wife bought an extra one, and I stole it to treat the wall behind and between my speakers with the result of a more focused center image and no hardness in the treble at volumes that previously over-energized my plaster walls. They'd be good at first-reflection points, too. Since they're a natural material, they don't look too bad either.