Grammarian PRO3 - Grammarian PRO3 is a feature-rich grammar checker that enables you to write better content without taking assistance from the English teacher.
Overleaf - The online platform for scientific writing. Overleaf is free: start writing now with one click. No sign-up required. Great on your iPad.
Gramlee.com - Online grammar check, proofreading and copy editing services.
TeXstudio - TeXstudio is an integrated environment for writing LaTeX documents.
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
LyX - LyX is a document processor.