The Gapminder World
If everyone else has seen this, sorry, but The Gapminder World is an amazing visualization of international statistics. The program lets you program the x and y axes (as well as color and size) to correlate to different statistics (like per capita income, birth rate, life expectancy or percentage of women in the work force). What you get is an amazing look at how the world has changed and a really cool way to surface historical insights. Apparently Google bought it last year and you can watch Hans Rosling, the director, talk about it at TED.