itch.io

Set in a fictional universe, often (but not always) with fantastic or supernatural elements, alternate worlds, magic and monsters.

An adventure where choices actually impact the story.

Focused on using its text, moreso than its visuals or audio, to tell the bulk of its story/plot. (Still can have great audio and visuals, though!)

Twine is a free and open source tool for telling interactive, non-linear stories.