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.
Expresso - The award-winning Expresso editor is equally suitable as a teaching tool for the beginning user of regular expressions or as a full-featured development environment for the experienced programmer with an extensive knowledge of regular expressions.
Novelize - Novelize is an online novel writing app designed to keep authors on track.
Writefull - Writefull provides you with the tools you need to improve the quality and consistency of your writing.
Manuskript - Open-source tool for writers.