Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
Ink by Inkle - ink is a popular open source scripting language for branching stories, designed for writers
Quest - Quest lets you create sophisticated text-based games, without having to program.
Squiffy - Squiffy is a tool for creating multiple choice interactive fiction.
RenPy - Ren'Py is a free and cross-platform visual novel engine that helps you use words, pictures, and...
Dedalus - Dedalus is an authoring system for generating Choose Your Own Adventure (CYOA) narrative.