Dabble Writer - Writing software for novelists.
Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
Novlr - Online word processor and organizer for novel writing.
RenPy - Ren'Py is a free and cross-platform visual novel engine that helps you use words, pictures, and...
SHAXPIR - A modern cloud workspace for fiction writing & worldbuilding
Quest - Quest lets you create sophisticated text-based games, without having to program.