CKEditor - Real-time collaborative future-ready rich text editor
Grammarly - Clear, effective, mistake-free writing everywhere you type.
TinyMCE - TinyMCE is a content editor that functions as a plug-in for Wordpress websites.
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Quill - Powerful, API-driven rich text editor
Editsaurus - Highlights potential pitfalls in your writing to encourage good habits.