Taking after Map of the Market, the New York Times uses tree maps to show a year of heavy losses by major companies. It's a pretty sad state of affairs. Content aside though, this is certainly one of the reasons the Times is so popular among the infographics crowd. Data visualization isn't just bar graphs and time series plots.
Anyways, back to the subject of the market. Look at the map of the market from today. Red means loss. I'm going to cry. No, not really, but still, it's sad. Okay, I'm crying now.