Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Sutle - Save and organize resources into a directed learning path.
ClassicPress - The WordPress fork. No Gutenberg. Great future!
Postly - Turn your photos into REAL beautiful postcards. Available on iPhone, iPad and Android. Make friends and family smile with a postcard!
TYPO3 - TYPO3.com - Infos, SLAs, Extended Support Versions and more
Developer's Guide to Content Creation - The book for devs who want to make quality technical content