From CS294-10 Visualization Fa07
 Good Visualization
I selected the following good visualization from Forsyth, D. A. and J. Ponce. Computer Vision: A Modern Approach. Upper Saddle River, NJ: Prentice Hall, 2003.
I recall that in most of my high school/undergraduate Physics & Calculus textbooks, the authors would only use words to explain the right-hand rule. I didn't really understand it until a teacher demonstrated. This visualization is effective because with the hand illustration, it is immediately clear how to utilize the convention.
 Bad Visualization
I selected this bad visualization from Jansen, B. J. and A. Spink. "Sponsored Search: Is Money a Motivator for Providing Relevant Results?" Computer Aug. 2007: 52-57. This magazine is published by the IEEE Computer Society.
I found the authors' method of distinguishing between sponsored and non-sponsored links to be unattractive and needlessly cluttered. They could have imparted their meaning equally well without drawing so many lines on the screenshot.