Many companies and people have very monotonous tasks that need to be done on a daily base. For example, image hosts may need to filter out explicit images or they may need to identify faces or objects in pictures. Computers are not so great at these tasks, so Amazon has found a way to outsource these tasks to normal web surfers like you and me and pay us a few cents for each little task. The place to do this is the website Mechanical Turk.
How does it work?
Once you've signed up, you can access a list of HITs (Human Intelligence Tasks). A HIT is a small unit of work that a requester has posted to the MTurk website. Example hits may include the following: (1) categorize 20 pictures as containing a person or not, (2) transcribe a minute clip of audio, or (3) fill out a brief survey. These are just a few examples, but you get the idea. Most good HITs will only take a minute or two to complete.
Once you have completed the HIT, you can continue doing more HITs. If you are good, you can get many done in a short period of time and this is really the key to making a decent amount of money.
How much will I make?
The short answer is, not much. If you really work at it, you can make a few dollars an hour. So, don't expect to quit your day job. However, if you have a lot of downtime during the day you can make enough to cover a few cups of coffee or a magazine. That's worth something, right?
How do I get paid?
Amazon pays you in two ways: you can either get Amazon gift certificated or have money transferred to your bank account through Amazon payments. I have found that the main limitation to getting paid quickly is not Amazon but, rather, the individual requesters. One of the drawbacks of MTurk is that requesters can choose to either pay or not pay you for the HITs you've completed based on whether they believe you accomplished the task correctly. However, if a HIT gets rejected you have no way of contesting the decision. This is frustrating, but on the whole not a major issue.
Hope that was helpful! Now, what are you waiting for? Go waste lots of time so you can make a few cents! If you know of other ways to make small change on the internet, leave it in the comments, I'd love to hear.