This "Self Portrait" ad from Martha Stewart Living Omnimedia reminded me of the 'good thing' I learned (from Martha, of course) several years ago.. keeping paint swatch stirrers. As you mix a can of paint, allow the wooden stir stick to drip into the can and then allow it to air dry. On the non painted portion of the stir stick, write the color, the finish used, what room, date painted, and manufacturer of the paint. Also include any 'recipe' for the paint color mix should it be available. Drill a small hole at the top of the stir stick and keep all your color swatches together using a binder ring, or tied with a piece of twine or leather lacing.