Joomla! is the world's hottest open-source content management system, and the winner of the 2006 Open Source CMS Prize. While Joomla! is packed with features, its greatest quality is that it is extremely extensible, allowing any number of complex applications to be cleanly integrated. Shopping carts, forums, social networking profiles, job boards, and real estate listings are all examples of extensions developers have written for Joomla!. All of these can run off one Joomla! site, while only one database, template, and core need to be maintained. When you build an extension to Joomla!, it...