Rock RMS - Rock RMS is a community supported open-source Church Management System that provides innovative features to churches of all sizes.
Bludit - Bludit is a web application to build your own website or blog in seconds, it's completely free and open source. Markdown support.
eCatholic - eCatholic provides a total content management system that helps Catholic parishes, ministries, & dioceses create websites & website design.
Grav - The modern open source flat-file CMS
ChurchInsight - ChurchInsight is a church website content management system (cms). It allows churches to have great church websites and the best church website designs.
HTMLy - HTMLy is an open source databaseless blogging platform. A Flat-File Blog and Flat-File CMS written in PHP prioritizes simplicity and speed.