There are so many social networking tools ranging from the huge well known sites like Facebook and LinkedIn to smaller niche networks that share hobbies. These superseded the very popular MySpace and Friends Reunited.
Wikipedia has a comprehensive list in alphabetical order rather than genre. https://en.wikipedia.org/wiki/List_of_social_networking_websites.
There is also a list of defunct social networking sites https://en.wikipedia.org/wiki/List_of_defunct_social_networking_websites
There are many other tools which are arguably under the umbrella of social networking tools. Tools such as Twitter and Instagram have their own tab. Others like SnapChat for example are listed in the Creating – Photos tab.