I finally went out and bought the brand new book called The Hot Shoe Diaries, by Joe McNally. I heard about it on a recent TWiP podcast. The book is amazing, what i have read so far. It is entirely devoted to getting the most out of a single flash, and later with multiple flashes.
I have always been a little weird about using flash at all. I hate the look of flash pictures, but if you know how to really use one they can be great. This book, in the first 50 pages or so, has taught me more about flash work than i have ever know.
So, if you would like to learn how to use flash more creatively, or even just in general, definitely check out this book. It is by far the best i've read about the topic.