Bludit - Bludit is a web application to build your own website or blog in seconds, it's completely free and open source. Markdown support.
ApPHP AdminPanel - ApPHP AdminPanel Website Back End Script
Grav - The modern open source flat-file CMS
CushyCMS - CushyCMS is a FREE hosted content management system that's actually easy to use, fast to setup and doesn't require programming skills.
WonderCMS - WonderCMS is the smallest flat file CMS. Completely free, open source, privacy oriented for over 12 years.
P4A - Php For Applications - PHP5 RAD Framework based on Zend Framework.