Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
OptiLingo - OptiLingo: Dreaming of Speaking a New Language?
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Mondly - Learn 33 languages in 500 bite-size lessons and 14 conversational modules.
Editsaurus - Highlights potential pitfalls in your writing to encourage good habits.