This is a browser extension you can install that will occasionally show you sponsored advertisements on your sidebar when you search. Each advertisement is worth a few cents or more. If you visit the ad shown, you receive the dollar amount shown in your Qmee virtual “piggy bank”. You can cash this out at anytime, there is no minimum. Also, the money shows up in your Paypal account pretty much instantly after you ask for it. I put this site on this list because even though it's not a big earner, you can get paid quickly.
Last but not least, you can also earn money online by building an online community, although the monetization strategies you can pursue will vary a lot depending on your goals. You can build a community with a blog, for example. You can also build an online forum and charge people for membership. You could even build up a Facebook group and use your influence there to sell and promote products.
If you have a good idea for an app, and the skills to create it, then producing your own premium app can be profitable. However, with so many free apps available, it may be hard to convince people to pay. If you want to go down the premium app route, consider having a basic free version to encourage people to download the app in the first place. You can then provide the option of upgrading to a premium plan once users realize how useful the app is.