ThredUP sends you a free Clean Out Kit to fill with all the gently used, on-trend clothes you no longer wear. They'll take care of everything else, including professionally photographing your items and listing them on the site. You receive an upfront payout once the items are processed, or if it's a unique item, you'll be paid once it's sold. Payouts are offered in the form of ThredUP store credit or donation to a cause, or you can transfer the cash to PayPal.
Fiverr. This is a popular website that can be helpful for freelancers with actual skills. Know something about digital animation? You can work for someone who doesn't and pick up some extra cash. But if you just have a brain but few skills, you can offer to do web research for someone, and maybe someone will hire you. Just know that you probably aren't going to get rich doing these jobs. The website's tag line is, "Freelance services for the lean entrepreneur," which tells you right away the pay is – meh. Plus, the website's name comes from the fact that many people work for $5 per task (but, yes, you can ask for more). Still, if you get a lot of gigs, it can add up.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.