Bludit - Bludit is a web application to build your own website or blog in seconds, it's completely free and open source. Markdown support.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Grav - The modern open source flat-file CMS
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
WonderCMS - WonderCMS is the smallest flat file CMS. Completely free, open source, privacy oriented for over 12 years.
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.