Why drop 10 or 20 bucks on a fabric drop cloth when you've got stacks of cardboard in the garage? Cardboard can act as a drop cloth during painting or furniture staining projects. The thickness and texture of corrugated cardboard keep water and other substances from leaking through, making it an ideal surface protector.
Temporary placemats can also be created with just a few rectangular pieces of cardboard and a pretty covering (such as shelf paper or fabric). Virtually any surface can be covered and protected using cardboard. Even if something is spilled on it, the cardboard can still be recycled or used for another purpose. Now that's thinking green -- and smart!