Grav is a modern open source flat-file CMS
Hugo is a Fast and Flexible Static Site Generator
Jekyll is a simple, blog-aware, static site generator.
Nesta is a Ruby CMS for developers and designers.
PhileCMS is a file-driven CMS. Powered By Markdown And Twig. But You Can Change That.
PieCrust is a static website generator and flat-file CMS.
Sculpin is a static site generator written in PHP.
Stacey is a lightweight content management system.
Statamic is Comercial FFCMS.