The Drupal Content Management System is one of the most popular Content Management Systems available. It's modular design makes it flexible and extensible, and thousands of modules are available for any purpose - from personal blogs to large eCommerce sites.

The built in support for Taxonomies, the additional Content Construction Kit and the Views modules make it a powerful platform for managing large amounts of content.

Specialist systems, such as the ProsePoint newspaper publising system, the Open Atrium "intranet in a box",  and the Deanspace CRM (now CiviCRM) have all been built on Drupal.