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
Yarn Spinner - Tool for creating interactive dialogue and games in Unity.
Dedalus - Dedalus is an authoring system for generating Choose Your Own Adventure (CYOA) narrative.
ADRIFT - Create your own Interactive Fiction with this free, easy to use application for Windows.
Squiffy - Squiffy is a tool for creating multiple choice interactive fiction.