Drupal open source content management system (CMS) written in PHP and distributed under the GNU General Public License is an excellent tool to help you build an efficient and scalable web site. It is used as a back-end system for at least 1% of all websites worldwide ranging from personal blogs to larger corporate and political sites including whitehouse.gov and data.gov.uk, making it perfect for any business no matter how big or small. It can also be applied as a knowledge management or business collaboration system.