Write and publish an eBook. You don’t need a traditional publisher and financial backing to publish your own book anymore. In fact, Amazon.com makes it possible for you to publish your own eBook and sell it independently – with no financial investment on your part. And with Kindle eBook publishing, your book will appear on Kindle stores worldwide within 24-48 hours. Just be prepared to market it yourself on social media, your blog, or elsewhere if you expect to generate sales.
Along the same lines as trivia, you can get paid for just using your mobile phone and allowing companies to know what you're doing on it. For example, Nielson Mobile Panel is an app that you can earn rewards on just for having it installed. It will take snapshots of what you're doing and use those for advertisers to know more about your demographic. It takes away some privacy, but you get paid for it.
Noticeably absent from my list is “blogging”. I enjoy blogging and sharing with readers ways to save money, inspiring success stories and of course geek culture. However, blogging is not the path to quick money online. Despite what many bloggers and peddlers of courses may suggest, blogging is very hard work and it takes a sizable audience to make even a modest return.