Grav is an easy to use, yet powerful, opensource CMS that requires no database. In a nutshell, installing Grav is a matter of unzipping the file. It is fast, has sophisticated caching, and a light footprint for optimal performance.
Publii allows to you build, modify and manage an unlimited number of sites from the same app with instant switching; no databases or other credentials to remember.
Bludit is a web application to build your own website or blog in seconds, it's completely free and open source. A PRO version is available for those who want to support the software developer. The software seems almost the same between the versions.
FlatPress is an open-source standard-compliant multi-lingual extensible blogging engine which does not require a DataBase Management System to work. You don’t need MySQL because FlatPress stores all of its content on text files.
GetSimple is an XML based lite Content Management System. To go along with its best-in-class user interface, we have loaded it with features that every website needs, but with nothing it doesn't. GetSimple is truly the simplest way to manage a small-business website.
Vapid is an intentionally simple content management system built on the idea that you can create a custom dashboard without ever leaving the HTML.Discontinued
Backdrop CMS is a simple, lightweight, and easy to use Content Management System used to build attractive, professional websites. Use it for everything from a single-administrator's personal blog site, to a complex, multi-role, business e-commerce platform.
HTMLy is an open source databaseless PHP blogging platform. A flat-file CMS that allows you to create a fast, secure, and powerful website or blog in seconds.