Here are some open source social networking software that you can use to set up your social networking website,
Mahara is an open source e-portfolio, weblog, resume builder and social networking system, connecting users and creating online learner communities. Mahara is designed to provide users with the tools to demonstrate their life-long learning, skills and development over time to selected audiences.
Elgg is an open, flexible social networking engine, designed to run at the heart of any socially-aware application. Building on Elgg is easy, and because the engine handles common web application and social functionality for you, you can concentrate on developing your idea.
Built with Ruby on Rails, Lovd is a social networking solution that has everything you need to build your community.
People can connect to a group to contribute using OpenID. They get tracking tools such as forum digest and blog RSS feeds.
Dolphin Smart Community Builder is a universal, free, open source software that allows you to build any kind of online community. With a huge variety of features & options, you can quickly develop your very unique and successful website.
PHPizabi is another social networking software in PHP.
Insoshi is a product and a project. The product aims to be the best open-source social networking platform. The project is to make the product!