Dialogue Designer - An easy to use but powerful tool for creating branching dialogues for games.
Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
Arcweave - Arcweave is the first browser based cloud professional tool for game and narrative design.
RenPy - Ren'Py is a free and cross-platform visual novel engine that helps you use words, pictures, and...
TalkerMaker Deluxe - A FOSS Branching Game Dialogue Editor
Quest - Quest lets you create sophisticated text-based games, without having to program.