ProWritingAid - For the smarter writer. A grammar checker, style editor, and writing mentor in one package.
Ginger - Powerful and effortless desktop & mobile solutions for improving your writing and productivity. Ginger Software is your personalized editor - everywhere you go.
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
PaperRater - Grammar & Spelling Check; Free Online Proofreading; No Downloads...
Readable - Readable.io is a collection of readability and writing tools to help improve the quality of website and document content.