Drupal is a free software package that allows an individual or a community of users to easily publish, manage and organize a wide variety of content on a website. Tens of thousands of people and organizations are using Drupal to power scores of different websites, including Community web portals, Discussion sites, Corporate websites, Intranet applications, Personal websites or blogs, Aficionado sites, E-commerce applications, Resource directories, Social Networking sites.
Drupal is an open-source software distributed under the GPL (“GNU General Public License”) and is maintained and developed by a community of thousands of users and developers.
To learn about Drupal go to http://www.drupal.org