I personally like this one for some spare cash. It does not take much to earn an extra $20 – $50 a week. Some claim that they are able to make a living by dedicating their time to different jobs at mTurk. You will have to go through a learning curve, but once you get comfortable, you will find plenty of good and interesting HITs (Human Intelligence Tasks) to work on.
I’m using a free method as a result of my own researched to discover high value sites online for basically anything. The important thing is to tell Google what you’re looking for. Something like “Free Online Survey Sites That Pay”, then check page rank, and then both quality and quantity of visitors. You will find the article on how to apply this method on my Blog Titled – 2 Simple Research Tactics For Exponential Visitor Conversion At No Cost
Upwork: This website offers a great marketplace for selling just about any professional service. You don't need a merchant account, website of your own or anything else for that matter. All you need to do is be able to provide a high-quality service at a reasonable price. But be informed, you will have to compete with many others that are constantly bidding on open jobs.
For example, let’s say you signed up to become an Amazon Associate so you can make money as an affiliate of Amazon. You then create a gardening video showing people how to plant a small tree. Find the exact shovel you are using in the video, on Amazon, get your affiliate link and put it in the description of your video so people who are interested can buy the same shovel on Amazon. For every person that buys the shovel, you earn a commission.