I came across an amazing blog that is called Presentation Zen. This link brings you directly to the highly informative and entertaining post "Gates, Jobs and the zen aesthetic". I am amazed at how knowledgeable and talented the creator of this blog is. He offers wonderful guidance on creating beautiful and effective presentations.
I once collected my own personal "Gallery of Horror" Powerpoint slides that unfortunately came directly from my clients’ laptops. I must dig them out and share some with you, since they truly boggle the mind in their horrible design.