CKEditor - Real-time collaborative future-ready rich text editor
TinyMCE - TinyMCE is a content editor that functions as a plug-in for Wordpress websites.
Edtr.io - Intuitive WYSIWYG web editor, open source & fully adaptable.
Trumbowyg - Feature-packed WYSIWYG editor in only 15kB of JavaScript
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
Aloha Editor - Aloha Editor is an HTML5 WYSIWYG Editor that gives you a total new experience when editing.