The Head First folks discuss their techniques for using graphics to make a document easier to read. My favorite: "Pretend that for some reason you cannot use words to make your point."
Their whole site is good.
This is BrainLog, a blog by Dan Sanderson. Older entries, from October 1999 through September 2010, are preserved for posterity, but are no longer maintained. See the front page and newer entries.
November 28, 2006