Writer’s block is probably one of the biggest problem faced by many aspiring authors today. iMuse, which is available in the Mac App Store, aims to solve that problem by giving you a place to store all your notes and photos before and during writing so you’re never short of ideas.
You can also define keywords in the text, from which the app will then find related articles on Wikipedia and photos on Flickr.
The app is completely free, so it’s worth giving it a shot, especially if you’re short of ideas when writing a book.