Grammarly - Clear, effective, mistake-free writing everywhere you type.

LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.

SentenceCheckup.com - SentenceCheckup can check for run-on sentence structure and fragment, As well checkup for grammar, punctuation and style issues.

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.

Editsaurus - Highlights potential pitfalls in your writing to encourage good habits.

Ginger - Powerful and effortless desktop & mobile solutions for improving your writing and productivity. Ginger Software is your personalized editor - everywhere you go.