JomSocial is a social publishing platform for Joomla! content management system. It allows you to connect with friends, integrate videos, follow users' activity stream, share photos, create groups, and customize your brand.
JomSocial is an out-of-the-box extension that enables a Joomla! website administrators to set up a social network with ease, and customize it to meet the needs of a site. By the end of the book, the reader will have built a good looking, fully functional social networking site using this hands-on guide.

Comprehensive guide to creating Web sites with the open source Joomla!1.5
Joomla! is an open source content management system (CMS) for Web sites. While it is free and relatively easy to use, there are lots of tricks and functionality that may not be intuitive to new users or those switching from other systems.

Joomla is a free and open source content management system (CMS) for publishing content on the World Wide Web and intranets and a model view controller (MVC) Web application framework that can also be used independently.

Nowadays the web is becoming more and more social and while websites like FaceBook and Twitter are connecting millions of visitors each day, your next client for sure will request a social or community based website