I'm preparing a presentation to my co-workers covering findings from an Edward Tufte lecture I attended last month. Tufte is best known for popularizing the visualization of quantitative information. Below is the classic Joseph Minard graph drawn in 1861. Due to its age, its impact, and its detail, many call this the best graphical depiction of information ever drawn. I've seen "flashier" graphs than this, but I agree that this is very deep and very rich. It tells the story of Napoleon's ill-fated 1812 march to Moscow. The tan line indicates Napoleon's charging army, while the black line indicates his retreating army:
Tufte describes it as follows:
"Beginning at the left on the Polish-Russian border near the Niemen River, the thick band shows the size of the army (422,000 men) as it invaded Russian in June 1812. The width of the band indicates the size of the army at each place on the map. In September, the army reached Moscow, which was by then sacked and deserted, with 100,000 men. The path of Napoleon's retreat from Moscow is depicted by the darker, lower band, which is linked to a temperature scale and dates at the bottom of the chart. It was a bitterly cold winter, and many froze on the march out of Russia. As the graphic shows, the crossing of the Berezina River was a disaster, and the army finally struggled back into Poland with only 10,000 men remaining. Also shown are the movements of auxiliary troops, as they sought to protect the rear and the flank of the advancing army. Minard's graphic tells a rich, coherent story with its multivariate data, far more enlightening than just a single number bouncing along over time. Six variables are plotted: the size of the army, its location on a two-dimensional surface, direction of the army's movement, and temperature on various dates during the retreat from Moscow."
Below is another good example that he points to from the New York Times. Despite the message it's trying to convey, it does a good job of graphically telling a story. It's causal and explanatory, it includes sources, and it makes you want to learn more: