WordPress–WordPress CMS is more popular amongst webmasters and online business owners alike. Not only does it comes free of cost but is also easy to install.

Joomla–Besides being used as content management system, it is also used for creating applications. It is also an open source platform and you have shell out no money for using it.

Frog CMS–Frog CMS is a PHP edition of Radiant CMS and is based on the Ruby on Rails application. Professionals who make use of this CMS should have thorough understanding and knowledge of this scripting language as it makes use of PHP.  

Drupal–It is another most popular software application available today. Websites such as MIT and Sony Music are driven by it.