WordPress is a free and open source blogging tool and content management system (CMS) powered by PHP and MySQL. It has many features including a plug-in architecture and a template system. WordPress is used by over 14.7% of Alexa Internet's "top 1 million" websites and as of August 2011 powers 22% of all new websites. WordPress is currently the most popular CMS in use on the Internet.
Drupal ( /ˈdruːpəl/) is a free and open-source content management system (CMS) and content management framework (CMF) written in PHP and distributed under the GNU General Public License. It is used as a back-end system for at least 1.5% of all websites worldwide ranging from personal blogs to corporate, political, and government sites including whitehouse.gov and data.gov.uk. It is also used for knowledge management and business collaboration.