LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Grammatica - AI powered writing assistant
Grammarly - Clear, effective, mistake-free writing everywhere you type.
Linguix Writing Coach - Improve your language skills while writing online
WhiteSmoke - WhiteSmoke software products for writing and language. WhiteSmoke is a grammar checker, spell checker, style checker and more - in a single package. Also featuring translation software and English video courses.
Anyword - An AI platform for creating effective marketing copy, trained on tens of millions of successful ads.