CKEditor - Real-time collaborative future-ready rich text editor
Apple iWork - iWork is an office suite by Apple.
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
Airborn - Create and edit documents online without sacrificing your privacy
Froala Editor - Froala Editor is a WYSIWYG HTML editor that enables rich text editing capabilities for the applications.
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.