How often have you dropped change in a public place and didn't bother to pick it all up? How many times have you found coins or even cash while walking from your car to the store? It does happen on occasion and we could find a lot more free money just lying around if we were actually looking for it. Some places are better than others when trying to find money, it's just a matter of taking a closer look.
The Sidewalk - When you're walking from place to place, keep an eye open for change, especially near parking meters and self pay parking machines.
The Laundromat - People are using coins all day at the laundromat and at some point, some are dropped and never picked up. Be sure to check around the washers and dryers and also near the snack and change machines.
Vending Machines - You don't have to reach inside every coin return slot. People drop coins around vending machines all the time.
Stores - It's logical that people are going to drop money near registers. I do it all the time. Run your foot along the outside edge of the end caps and the edge of the shelves going down the lane. Sometimes the money is there, but not in plain sight.
Parking Lots - When walking from your car to the store and back, take a little time to check the ground. I've found money in parking lots numerous times, especially where the lot meets the sidewalk entrance of the store and around the cart return areas.
The entire eHow article is here