There is an app called "Receipt Hog" which allows you to take pictures of your shopping receipts with your smartphone and gives you points for doing so. Points can be redeemed for Amazon gift cards, cash toward your VISA or toward your PayPal account. All receipts can be looked up and viewed later if needed. Although you won't make points very quickly unless you purchase a lot and scan everything, it will still add up over time. While it does let you scan receipts from anywhere, not all will be eligible for points. Receipts from certain stores, which are listed in the app, are preferred for getting extra points and slot spins.
There are also extra bonuses, like weekly spins of their slot machine for a chance to win free coins. You also get entered into monthly sweepstakes where you have a chance for bigger reward point wins. So far, after a few months of using this app, I have only won a handful of points from the slots and nothing from sweepstakes. The app lets you customize your pig avatar with different purchasable skins, don't be tempted by this, as it's obviously just a ploy to make you waste points.
The only problems I've come across with this program so far is that I have occasionally not scanned the entire receipt and it can't seem to find certain elements (like purchase date or whatever) even though I can clearly see it in the image. Also, one out of every 10 scans or so will fetch the wrong number from the receipt as the total. In these cases, you have to click on the "Report a Mistake" button when viewing your receipt. As mistakes have to be fixed manually by humans, this could take a day or two.
While this app is nothing groundbreaking as far as making extra cash, it does serve the extra purpose of archiving your receipts for you, which could come in handy if you need to look something up later and the paper receipt is lost. Give it a shot if you do a lot of shopping and get in the habit of scanning as soon as you come out of the store and into your car. Points can add up quickly. Get the app in your smartphone's app store.