1. Wordpress

WordPress is open source free CMS that is the best suitable for creating blogs, small business websites and corporate sites.
WordPress is easier content management system than other free CMS software. Anyone can quickly learn WordPress because there are many free resources available on the web.
Many free WordPress themes and Plugins can be download from WordPress directory. You can create a website of any context such as creative portfolio, business, eCommerce store, community, non-profit organization site, and so forth.

2. Joomla

Joomla free content management system is the best for building large ecommerce websites. In terms of coding power, Joomla is challenging CMS for beginners.
Website Creators who are looking to build powerful online applications, Joomla is best for you.
Joomla has a lot of free extensions and templates that allow you to customize your sites.

3. Drupal

Drupal comes with deeper open source content management system features and best for enterprise website and government websites.
You can create, manage and organize a wide variety of content on a website.
Drupal has more than 30,000+ extendable modules and 2,000+ themes that make your website handling much easier.