Joomla

Joomla! is a free and open source content management system for publishing content on the World Wide Web and intranets as well as a model–view–controller (MVC) Web application framework. It is written in PHP, stores data in MySQL and includes features such as page caching, RSS feeds, printable versions of pages, news flashes, blogs, polls, search, and support for language internationalization.

Within its first year of release, Joomla! was downloaded 2.5 million times. Over 5,000 free and commercial plug-ins are available for Joomla!.[2]
From Wikipedia, the free encyclopedia - http://en.wikipedia.org/wiki/Joomla