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.
CKEditor - Real-time collaborative future-ready rich text editor
Microsoft Word - Microsoft Word is a commercial word document processor for Windows.
Edtr.io - Intuitive WYSIWYG web editor, open source & fully adaptable.
Apache OpenOffice Writer - Open-source word processor of the Apache OpenOffice suite.
TinyMCE - TinyMCE is a content editor that functions as a plug-in for Wordpress websites.