Twine lets you organize your story graphically with a map that you can re-arrange as you work. Links automatically appear on the map as you add them to your passages, and passages with broken links are apparent at a glance. As you write, focus on your text with a fullscreen editing mode. Rapidly switch between a published version of your story and the editable one as you work. Twine is free to download and use, and you can share it with anyone you like.
The following videos will give you an idea of what twine is all about.