I really like this visualization of the US Income Tax Brackets for 1910-2010 (click on the image to the right to get a bigger image). It shows a lot of information in a manner that can be easily used for multiple types of analysis. It uses color well, i.e., using a simple sequential scheme. It uses inflation adjusted dollars. It uses a logarithmic scale. It places sources of information and credit for the work right on the graphic. It even basically shows how marginal tax rate works.

Good visualization doesn’t have to be flashy.