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.

18. CraigsList – Some things don’t ship very well. Other things may make you feel uncomfortable to sell to someone across the country. Anytime you’re selling a large item or something you just don’t want to ship, Craigslist is a great place to go. It’s simple to list your item (again, take good pictures!). If you don’t like the idea of putting your phone number out there, the interested individual can send you a message to your inbox without even getting your email address.
Considering that you have a finite amount of time, passive income should make up a large part of your work. If you're serious about generating any semblance of income online, then passive income should be one of your sole goals and ambitions. Why? Wouldn't you prefer to do the work one time and get paid repeatedly as opposed to relying on your time to generate that income? Invest the time at the front-end so that you can reap the benefits on the back-end. This means putting in a bit of sweat equity and not getting paid today. Rather, you'll get paid somewhere down the road. And you'll continue getting paid whether you keep building that passive income stream or you stop. 
Job well done, Satrap. The first thing I look for in a site like this are signs that the author is being paid to hype the companies. It’s very tough to find good information that isn’t stricken with bias. There were a couple of times during the article where I actually got excited thinking, ‘Hey, I could do that. I’d actually LOVE to do that.” That being said, I can’t help noticing that you refer to all of it as “extra” or “supplemental”income. Are you saying that with all of these options, sticking to one’s regular “day job” is required? In your experience, if someone really commits to doing this, is it possible to earn a decent living? Cubicles suck.
I’ve also seen a repeat of this article several times on this website. I find that rather questionable, to be honest. What I need is something to make a quick and *instant* 25-30 dollar, as in available *tonight*. Without putting any money down. Now, if you can point me to something that is 100% working in that manner, then that’s fine. Until then, you should rephrase your Google analytics so these articles stop appearing in searches for “immediate” and “instant” money. Thanks.

Mechanical Turk: Amazon's Mechanical Turk is a resource for doing human-intelligence tasks, or as the site commonly refers to them, HITs. You get paid a very small fee for any given HIT and you'll need a good deal of volume to make a substantial amount of money. But it is a resource you can use in your spare time to generate a small income online. 
What makes making money as an online English teacher particularly interesting and easy with sites like VIPKID is the fact that you don’t have to spend any time or money trying to find paying clients. VIPKID is a huge platform with hundreds of thousands of paying students. The site takes care of everything for you. Bringing you students, scheduling classes, pay, etc. All you have to do is set up your own schedule (yes, you get to decide when you want to work!) and teach during those hours.
You can sell your ebooks through Amazon's Kindle program or Apple's iTunes Connect, which gives you access to a large majority of the digital-book reading market and the barriers for entry are incredibly low. You don't need to invest lots of money to make this happen, but you do need to invest lots of time, not only in writing the ebooks, but in marketing them as well.
17. Amazon – Have you heard of FBA? It stands for “Fulfilled by Amazon” and it’s getting pretty popular. Basically, you buy products (in bulk is best) and ship them to Amazon for them to store. When your products sell, Amazon packs them up, ships them out and sends you the money (after taking their cut). There are people making a full-time living from FBA, while others just do it for some extra money.
The Field Agent app is available on Android and Apple devices. You only need to look for tasks within your area, do the research, submit the details of your findings and wait for your money. These tasks are simple and involve visiting stores and checking on issues such as display compliance, demos, and shelf availability. Each job may give you earnings between $3 to $12.