If you're serious about making money online, start a blog. Blogging is one of the easiest and most sustainable income sources. As long as the blog is setup the right way, in the right niche, with the right content targeted at the right audience, and the offer is complementary to the content, you could make a tremendous amount of passive income from a blog.
Amazon Mechanical Turk is a service that lets you make money online through doing paid microtasks. Each task is something simple that requires human interaction like rating search results, checking for the right spelling on search terms, categorizing the tone of an article, or even basic translating. You can do these tasks from anywhere you want and make money online from the world’s largest e-retailer.
Clickbank makes it super easy to get your own product online and literally puts it in front of thousands of affiliates that are skilled enough to make tons of sales. Most people think that their only option is to become an affiliate and promote the Vendor's product. If you have skills or knowledge that others can benefit from - then why not create your own product?