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.
References
From local businesses to global corporations, diverse organizations use Drupal.
News Publishing:
New York Observer, NowPublic, Popular Science, Economist
Intranet/Corporate Websites:
AOL Corporate, Dahon Bicycles
Education:
San Jose State University, Harvard, MIT, Council on Writing Program Administrators
Art, Music, Multimedia:
MTV UK, Sony Music, Warner Brothers Records
Community Portal Sites:
Fast Company, Team Sugar, Ubuntu Brainstorm
Social Networking Sites
DrupalSN, Jewcy