Batflat - Lightweight, fast, easy, and free CMS.
Joomla Video Plus Theme - Video Plus is a free joomla template suitable for building a video sharing website.
Drupal - Drupal - the leading open-source CMS for ambitious digital experiences that reach your audience across multiple channels. Because we all have different needs, Drupal allows you to create a unique space in a world of cookie-cutter solutions.
dotCMS - Java-based content management system
Joomla - Joomla! is the mobile-ready and user-friendly way to build your website. Choose from thousands of features and designs. Joomla! is free and open source.
SilverStripe - Make Digital Transformation happen