This fantastic lecture by Harvard cognitive psychologist Steven Pinker has a place of honor among the resources about visualization, infographics, and journalism I've gathered in the last fifteen years. In it, Pinker discusses the main points of the book he's currently working on. Watch it and notice how many times you can insert the words "visualization" or "infographics" instead of "writing." The lecture is supposed to be just about the effective use of language, but many of its lessons can be applied to visual communication.
Pinker recognizes he's been inspired by Clear and Simple as the Truth, by Francis-Noël Thomas and Mark Turner, a most excellent book about classic prose. Yes, that's another recommendation. After all, great visualizations aren't just the result of designing effective visuals, but of pairing words and graphics seamlessly.
(Side note: How is it possible that someone who knows so much about perception and cognition —and who has written about graph design— uses slides that are so poorly designed?)