The Joomla content management is extremely popular due to its comparitive ease-of-use and enormous flexibility.  Along with this popularity comes a huge community of knowledgable Joomla users, many of whom give of their time and energy freely to help others make the most of Joomla.  The product is under active development, and has consistently managed to keep abreast of improvments in technology to provide one of the most robust, secure, and feature-rich CMSs in existence - and it's free!

Joomla boasts the following features:

• A large and active user and developer community.
  Provides a basic level of content approval for registered users.
  Online help.
  Page caching mechanism to improve performance on busy sites.
  Trash manager (like a 'recycle bin').
  Advertising management (banners, etc).
  Media (images, documents) upload and management.
  Content display scheduling.
  Content syndication (RSS).
  Search engine friendly (SEF) URL's.
  Internationalisation (interface translation).
  Content macro language (aka mambots).
  Advanced and separate system administation.
  Advanced package/addon/template deployment system.
  Simple but powerful template system (written mostly in HTML, no complex templating syntax to learn, just a couple of PHP functions to include).
  Heirarchial user access groups.
  Basic visitor statistics.
  Multiple WYSIWYG content editor support.
  Simple polls.
  Content voting/rating system.

Many a great many free addons available. Some of these addons include:

• LDAP authentication
  Extended user profiles
  Forums
  Media galleries
  Document managers
  Templates
  Events calendar
  and many, many more...