StoryMill - Developers and publishers of Mac, Win, and iOS productivity, home and office and writing software such as MacGourmet, Paperless and many more. Based in MN.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
BlankPage - Stay motivated to write, and finish your story
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Manuskript - Open-source tool for writers.
ProWritingAid - For the smarter writer. A grammar checker, style editor, and writing mentor in one package.