Here are two websites from the IBM Research mathematician and hard-core data visualization expert Martin Wattenberg.
NameVoyager is a well-designed map of baby name popularity versus year. As you type, the graph arcs and swoons into shape. (Okay, I don't know what I thought the verbs "arc" and "swoon" signify in this context.) According to IBM Research, Mr. Wattenberg developed the site to publicize his wife's book, The Baby Name Wizard.
Map of the Market from SmartMoney depicts company stock performance by color, and the companies are spatially grouped by industry. Green squares represent rising stock price; shades of red represent falling stock price.