Batflat - Lightweight, fast, easy, and free CMS.
Grav - The modern open source flat-file CMS
nCMS - Open source enterprise Java CMS engine
WordPress - WordPress is web software you can use to create a beautiful website or blog. We like to say that WordPress is both free and priceless at the same time.
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.
Fansoro - Fansoro is a Modern Open Source Flat-File Content Management System.