Drupal

Drupal is one of the most popular content management systems. It is modular, extensible, customizable and powerful. Unlike Joomla!, which uses Object Oriented Programming (OOP) approach, Drupal uses fully procedural approach. Drupal’s code base is minimal and simple to understand. Like Joomla! you can develop modules (equivalent in Joomla! is called extension) to extend Drupal’s functionalities.