If you live in an area where Uber or Lyft operate, why not become a driver? If you're looking to make some short-term cash, you can definitely rake it in by working for one of these popular car-hire apps. As long as your vehicle fits within the specifications of their program, and you have a clean license, you could do this on the side, especially if you're in a crunch for cash.
Creating space for banner ads on your website is another way to generate a revenue from adverts. However for this type of advertising you will need to contact businesses directly and ask them if they would like to advertise on your website. The upside is that you can charge a set amount, or even a recurring monthly fee, to business to promote their services on your site. Using a WordPress plugin like AdSanity is an effective way to manage this type of advertising.
Find a profitable niche. Starting with your interests, write down as many niche ideas as you can. Think about topics people might search online. Ideas include passions (like surfing or body building), fears (like spiders or speaking in front of crowds) and problems (like getting out of debt). Do keyword research to see it others are interested in the topic. Find out if a domain name is available that matches the keyword 100 percent. 
Starting a podcast, like making a YouTube channel or blog, comes down to telling interesting stories and building an engaged audience. I’m probably sounding like a broken record by now, but you need a niche that you’re interested in and there’s already a demand for. Come up with a list of topics you’d like to talk about and then search iTunes charts, Google Trends and other podcast research sites like cast.market to see what’s currently out there and popular.
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.
Here’s a good example of how lead sales can work in real life: My second website, Life Insurance by Jeff, brings in a ton of traffic from people who are searching the web to find answers to life insurance questions. While I used to have the website set up so I could sell these people life insurance myself, it was a lot of work to process all the different requests and clients. As a result, I started selling the leads I gathered instead.