getgrav
Modern, Crazy Fast, Ridiculously Easy and Amazingly Powerful Flat-File CMS powered by PHP, Markdown, Twig, and Symfony
picocms
Pico is a stupidly simple, blazing fast, flat file CMS.
getkirby
Kirby's core application folder
flextype
Modern Open Source Flat Files Content Management System.
kormyen
Simple bookmarks and notes