Selling blood….there are very few companies that buy your blood. #1 reason being MANY people willing to sell their blood are not the type of people you want to receive their blood, ie drug addicts (not everyone). And if you can find a company willing to buy your blood you can only give it every 56 days (for whole bood). The most common blood product that is bought is plasma and you can only do that every 28 days (in New York state …which won’t buy blood anyways).
If you have a fondness and talent for taking pictures you can make extra money online by becoming a stock photographer and selling your images to a stock photo company like ShutterStock or iStockPhoto. You’ll get royalties every time someone licenses an image you’ve submitted. To really be successful, build your own photography website to be able to showcase your portfolio and start getting higher-paid private corporate work.