We all use maps, paper, online, or mental. Even emotional I suppose. Writers use them for many reasons: to help outline a story, to add to the book as a cool feature, to deal with a bit of ATHD, or just as a way to procrastinate from actual writing.  

Barbara O'Neal has written an interesting article in Writer Unboxed that describes how our minds map to the world around us, using a specific neuron for each location.