Turn a beat up door or the back wall of a built-in bookshelf into an unforgettable focal point, by adding an eye-popping shade of paint. A little paint goes a long way—a $4 sample-size can (applyed with a $3 paintbrush) is often enough to coat a 4x4' area. Need more paint? A $10 quart-size can of paint covers four times the space for only twice the cost. Cost: $7-13.