articy:draft!

Manuskript is an open-source tool for writers, with outliner, character management, plot development, distraction-free editor, etc. OutlinerOrganize your thoughts and snippets in a hierarchical manner. Organize them as you wish, reorganize them on the go.

Organon is a plugin for LibreOffice and OpenOffice.

oStorybook is a free, open source novel-writing software for creative writers, novelists and authors which will help you to keep an overview of multiple plot-lines while writing texts.

An ultimate outlining software for story writers. It is aimed especially for screenwriters, but can be used as well as for outlining novels, tales and any kind of stories.

A new screenwriting experience brought to you by Amazon Studios. Write your screenplay and focus on the story with features like auto-formatting, offline writing, and import/export in your favorite file formats. Keep your scripts safe with unlimited, secure storage in the cloud. When you’re finished writing your screenplays, you can submit them directly to Amazon Studios for consideration!

True Novelist provides a way for authors to write their novel online, organize their story, view statistics about their project and writing habits, set goals, keep track of related research, and more.

Based on the Firefox engine, supports standards, visual storyboarding, production scheduling, publication & international languages MUI support. Free tutorials, videos & wiki are available from the site. There is a very helpful community too.

A fairly bare-bones FOSS alternative to applications like ChatMapper and articy:draft to allow for people who don't necessarily have the money to license those programs to still leverage branching dialogue in a clean and easy way.

Writer's Café is a set of power tools for all fiction writers, whether experienced or just starting out. The heart of Writer's Café is StoryLines, a powerful but simple to use story development tool that dramatically accelerates the creation and structuring of your novel or screenplay.

Chat Mapper is a tool for writing and testing nonlinear dialogue, especially for video games.

Part word processor, part database, StoryMill provides every author with the tools essential to writing a best seller: everything from project-wide annotations to centuries-spanning timelines, an industry first. StoryMill introduces aspiring authors to multi-level writing methods of tracking characters, scenes, and locations, while professional writers will appreciate StoryMill's time-saving ability to oversee and manage the full creative process with Smart Views. Built from the ground up for Mac OS X, StoryMill offers an innovative way to channel and fine tune the creative writing process. Although StoryMill provides an impressive array of features to help you write and track the details of your story more effectively, none of them are required! StoryMill is incredibly flexible: it can simply be a no-nonsense place to write and revise using its distraction-free full-screen and powerful annotations, or a complete database of every character, location, and scene that makes up your novel. »