yWriter - Free writing software designed by the author of the Hal Spacejock and Hal Junior series. yWriter6 helps you write a book by organising chapters, scenes, characters and locations in an easy-to-use interface.
Manuskript - Open-source tool for writers.
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.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Novelize - Novelize is an online novel writing app designed to keep authors on track.
Story Architect (STARC) - STARC - A smooth yet powerful screenwriting experience for devoted authors. With only wanted features and simple workflow it runs faster than all your previous apps combined.