"One of the greatest things I've ever done was complete Julia Cameron's The Artist's Way. If you're not familiar, there are three main principals: 1. Write three full, loose-leaf pages every morning. This can be anything you want (e.g. stream of consciousness, stories, venting, or journaling.) 2. Go on an 'artist date' every week where you do something related to your art completely by yourself. 3. Read the weekly essay (there are 12 in total) and complete the tasks at the end.
I recommend this to every writer I meet who is struggling with any sort of creative block. Since completing it last year, I must have purchased at least a dozen copies for other people." —Christian Nilsson
Get it from Amazon for $11.55.