Have a closet or garage that needs a coat of paint, but you don't want to shell out the $20 for it? There's a couple easy ways to find paint for pennies on the dollar, and they're closer than you might think.
The first place to look is the same place you'd go to pay full price. Any paint store will have cans of paint leftover from mistakes in the mixing process. When a customer comes in with a swatch of fabric or a flower petal to get a match, and he's not happy with the end result, the store has to eat it. What you get is a bucket of paint nobody else wants. To cut their losses, the store will often sell the paint at a deep, deep discount just to make it go away. Their loss, your gain.
The other great place to look is your local sanitation department. Most cities have specific divisions that deal with paints, since you can't just toss them in a landfill. In Alameda, CA, it's a garage full of five-gallon buckets of paint, wall to wall. They'll just let you take what you want in most cases. They have to dispose of it somehow anyway!