WordPress is the most popular blogging system in use on the Web, at more than 60 million websites. It was first released on May 27, 2003, by its founders, Matt Mullenweg and Mike Little, as a fork of b2/cafelog.
Joomla is a free and open-source content management system (CMS) for publishing web content. It is built on a model–view–controller web application framework that can be used independently of the CMS.
Drupal is a free, open-source web development platform for online content and user communities. Drupal powers some of the busiest sites on the web, and can be adapted to virtually any visual design. Drupal runs over a million sites, including WhiteHouse.gov, World Economic Forum, Stanford University, and Examiner.com.