I visited Disneyworld after Halloween Extreme and I picked up a book there called, "The Imagineering Workout" written by Disney Imagineers. It's page after page of helpful creative exercises to get your brain pumping and help you think outside the box. This is a GREAT tool for Haunters! I'd recommend it, especially if you sometimes find yourself "stuck" on a project. It is available on Amazon.
http://www.amazon.com/The-Imagineeri.../dp/0786855541