Drupal: a free, open-source CMS distributed under the GNU General Public License. Drupal is great for developers with a working knowledge of HTML and PHP and large corporate sites.
Joomla: another free open-source CMS. Joomla, like Drupal, is great for those with some level of technical proficiency, but fewer themes and plugins.
WordPress: the most popular free, open-source CMS on the web. Unlike Joomla and Drupal, WordPress is ideal for non-developers looking to develop a small personal or business site.
Business Catalyst: it is an all-in-one hosted Content Management System built for Digital Agencies and Business Owners. Its unified digital marketing tools allow you to build powerful websites that rank well, are easy to manage, and include the tools you need to run a successful online business.