Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
CKEditor - Real-time collaborative future-ready rich text editor
Anchor CMS - Free and lightweight blogging system
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
Textpattern - Textpattern is an elegant content management system that is free, open source software.
Froala Editor - Froala Editor is a WYSIWYG HTML editor that enables rich text editing capabilities for the applications.