CMS

Drupal is a very powerful content management system (CMS)
Examples of sites that use Drupal

• economist.com, The Economist
• whitehouse.gov, The Whitehouse
• mtv.co.uk, MTV UK
• london.gov.uk, Greater London Authority
• nysenate.gov, New York State Senate
• greenpeace.org.uk. Greenpeace UK
• http://amnesty.org Amnesty International

And you can find many more here http://websites.usandv.com/