Drupal

Drupal is a PHP-based content management system and blogging engine which was originally written by Dries Buytaert and is the software used to power Debian Planet [1] and Kernel Trap [1].

Drupal is the English pronunciation for the Dutch word 'druppel' which means 'drop'.

While it is basically a SlashClone it has adopted a premise that "everything should be a node" which allows it to implement new features quite easily. You'll find modules for Drupal which do everything from currency conversion and photo galleries to mail list and CVS integration.

http://www.drupal.org/

Credit

The article is originally based on materials from infoAnarchy wiki and is updated as needed.