Index Card is a corkboard writing app that makes it easy to capture, organize, and compile your ideas. Whether you are an author, screenwriter, or academic researcher, Index Card can help you become a more efficient, organized writer. Download Index Card and discover why thousands of iPad owners are already using it.
I've been using Index Card since it first came out. It's my second-favorite iPad app -- first favorite is the Kindle app.
Not only is it wonderful for structuring your books, it's wonderful for capturing quick thoughts, and planning projects. If you enable the Long Text field, you can write complete scenes, or articles.
Disclosure: I have no financial or other interest in the company. I just enjoy the product.