Grammarly - Clear, effective, mistake-free writing everywhere you type.
Outwrite.com - Write better everywhere with Outwrite's proofreading and paraphrasing tool.
GrammarChecker.net - Grammar Checker is an online spell check tool. It effectively works on English sentence correction, Punctuation mistakes of 28 other different languages.
OpenKM.us - OpenKM is a document management software that integrates all essential document management into one easy to use solution.
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Grammarian PRO3 - Grammarian PRO3 is a feature-rich grammar checker that enables you to write better content without taking assistance from the English teacher.