Dabble Writer - Writing software for novelists.
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.
Microbit - BBC's handheld, programmable computer given free to UK kids
Novelize - Novelize is an online novel writing app designed to keep authors on track.
Novlr - Online word processor and organizer for novel writing.
Manuskript - Open-source tool for writers.