Double check yourself, before you double wreck yourself. Make sure everything you send to a company, whether a résumé, an email or a portfolio, is good to go. Double check your grammar and wording, and for God’s sake use spell check! This is especially important when it comes to the company’s name. Don’t spell their name wrong and be sure to type it how they type it (e.g. Problogger, not Pro Blogger).
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. 
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.

Alibaba is a Chinese eCommerce store that matches Chinese suppliers with buyers all over the world. Prices are extremely cheap, providing the possibility of large profits. However, with the potential profits comes more risk. As you are dealing with suppliers in China, if the quality of the product that arrives isn’t up to standard there is little that you can do about it.
Salvage and resell. Do you love antiques or have a knack for finding valuables at flea markets or yard sales? If you do, it might be time to consider salvaging items for resale – or even scouting out antiques to sell for a profit. While you’ll need to spend quite a bit of time searching for prospects and spend some money buying upfront, you could easily turn a profit if you know what you’re doing.
Donating plasma can actually work out better than selling your blood.  It takes longer to donate plasma because they will put your red blood cells back in your system. The upside is that you can donate plasma as much as twice a week and you can make anywhere from $40-$60 per donation. You can make that $100 in less than a week if you can stomach the needle.