As others have said there aren't really that many options when it comes to earning quick money. You'll find that a lot of quick money schemes can also be very risky so in the end, instead of actually making anything, you'll end up being worse off instead.
I'd say the best way to earn money quickly would be to have some variety of marketable skill. Let me explain, I have some fairly decent computer programming skills, and on the side I've been doing freelance programming jobs. One can easily make a few hundred dollars through freelancing if you have the proper skillset. Writing, Design, Programming, etc. Some marketable skill will give people the chance to make decent money. Though this is online most of the time, so admittedly not for everyone. Making money quickly that isn't online...ehhh Craigslist for jobs. Doing some variety of work there may be able to make some quick cash, but maybe not the best source. Naturally one could sell their possessions. Overall it isn't easy to make money quickly, but it is possible, but not in huge sums.
