While content management systems like WordPress and Joomla will support multiple blogs and multiple authors on a single blog, they are designed for relatively few actual sites--a dozen or so.
The collections here include base templates for WordPress, Joomla, and Mambo content management platforms as well as PHPNuke, PHP-Fusion and forum templates like phpBB and vBulletin.
There are many different kinds available for free, such as Joomla and Drupal, plus many out-of-the-box versions from larger companies such as Microsoft and Apple.
Strategies to Developing Websites describes the long list of CMS applications that allow you to easily expand a website, including popular tools like Joomla!
WordPress is one of the biggest and most flexible blogging and content management systems (though Joomla and Drupal are also very popular.
Joomla is a popular Content Management System (CMS), which offers tons of customizable features.
Some of the most popular ones are Joomla, Drupal, or Mambo.
Joomla templates are easily found online.