Grammarly - Clear, effective, mistake-free writing everywhere you type.
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.
Typely - A sensitive, unobtrusive and reliable tool for any writer, newspaper editor, teacher, blogger or student STA
Novelize - Novelize is an online novel writing app designed to keep authors on track.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Manuskript - Open-source tool for writers.