It comes as no surprise that this would be number one on the list. With Amazon.com around, there’s no need to leave the comfort of your home to buy anything that you need. It is the largest online retailer in existence. The website earns its revenue through its retail endeavors, cloud service, and digital ad services. In 2018, Amazon had a domestic gross of more than $7B. Its e-commerce business makes up close to half of online sales in the United States. Amazon has purchased more than 125 companies. Of course, it's safe to assume that many of those companies will soon be making their contributions to the website’s revenue stream.