bibisco - bibisco is a novel writing software.
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.
Manuskript - Open-source tool for writers.
Novelize - Novelize is an online novel writing app designed to keep authors on track.
WriteFreely - Write Freely is free and open source software for starting a minimalist, federated blog — or an entire community.
Nulis - Tree editor for writers, makes outlining your stories and articles easy, fun, and convenient.