I've been making a little bit of cash by selling my old college books on Amazon, and figured I'd recommend it to people who have some old college books or any books or electronics that they no longer care to have. It's a little bit of work but worth it. I save money by wrapping the book into a brown grocery bag (like a present), pay the cheapest postage possible, and depending the book, can make a small to medium profit. Of course, I base this off the USPS mailing system, so it might not be as worth it for those who don't have it... or might be even more worth it.
My father was kind enough to donate some of his fantasy books to me to sell and keep for myself, so I make a small amount of cash. My cousin also asked me to sell some of her college books and I cold get a a cut from the proceeds, and her books go for pretty high! Thanks to selling these books, I've been able to... well... pay some minimum bills and keep myself afloat until I can find a job. Worth checking out. if any question on it, I'd be willing to answer what I know.