Wikipedia: A webring is a collection of websites linked together in a circular structure, and usually organized around a specific theme, often educational or social. They were popular in the 1990s and early 2000s, particularly among amateur websites.
Methods of website linking - In the field of search engine optimization, link building describes actions aimed at increasing the number and quality of inbound links to a webpage with the goal of increasing the search engine rankings of that page or website.
Web directory - A web directory or link directory is an online list or catalog of websites. That is, it is a directory on the World Wide Web of the World Wide Web. Historically, directories typically listed entries on people or businesses, and their contact information; such directories are still in use today.
Article directory - An article directory is a website with collections of articles written about different subjects. Sometimes article directories are referred to as content farms, which are websites created to produce mass content, where some are based on churnalism.