Green Car Reports, R Q Riley Enterprises and 3-Wheelers.com have information about three-wheeled cars. The first two options have articles about them that cover the history and basics, while the third is entirely focused on vehicles with three wheels.
Green Car reports has a detailed history of three-wheeled vehicles that starts in the late 1800s with a three wheeled motorcycle. The article goes through the timeline, talking about important advances in three-wheeler technology. The information is supplemented by pictures, links to other sources and a related article section that lists other articles on the site centered around cars with three wheels.
R Q Riley Enterprises features a lengthy article that looks at the mechanical and technical details of three-wheeled cars, such as stability, build and responsiveness. The article also discusses different types of designs and gives them a brief review. A few images help illustrate some points, but the site is mostly text-based.
3-Wheelers.com has a comprehensive list of three-wheeled vehicles in alphabetical order users can browse for specific information. The site also has a collection of resources, such as books, articles, a history, trivia and galleries. Users can create an account and join the site's message boards to discuss three-wheeled cars with other enthusiasts.