Drupal is an open source content management platform powering millions of websites and applications around the world. It’s supported by an active and diverse community of people around the world, and is used by some of the biggest sites on the web including The EconomistExaminer.com and The White House

We like Drupal because it is highly versatile, offers a host of add-on modules, and allows us to get really creative.  It also integrates seamlessly with CiviCRM.