Drupal is a web content management system and web application framework written in PHP. It is also a vibrant, growing, and fun community of programmers, activists and communicators. The core Drupal software is a framework to power community driven web site software, and includes features such as internationalization, tagging, and an extensive roles and permissions system. The highly extensible architecture supports well over a thousand sub-projects in the form of contributed modules and themes, so there's something here for everyone.