Manuskript - Open-source tool for writers.
Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Ink by Inkle - ink is a popular open source scripting language for branching stories, designed for writers
Storyline Creator - An elegant tool for authors to write, organize and visualize their stories.
Arcweave - Arcweave is the first browser based cloud professional tool for game and narrative design.