Drupal is a completely free, open source content management system that many intelligent companies are using today to provide for their needs. Drupal's many features and add-ons allow it to be used for a variety of website needs; perhaps for marketing, internal communications, informational websites, or for social networking purposes.
If a needed feature is not currently available, it has a proven community of developers who can be paid to do the work for you. Drupal's access control system means that it can be easily applied to your organizational structure. Overall, Drupal is a good choice for today's companies of any size because it is free, easy, and incredibly flexible.
Tens of thousands of people and organizations are using Drupal to power scores of different web sites. Drupal is distributed under the GPL ("GNU General Public License") and is maintained and developed by a community of thousands of users and developers.