Many of you may be familiar with the excellent TED Talks given by Sweden's Hans Rosling about visualizing data. His tool, Gapminder, is an innovative Flash application that allows normally rather mundane data to come alive and reveal trends and patterns not normally seen. Gapminder was snapped up by Google in 2007. However, Gapminder's website still has some cool PDFs of visualizations as well as access to some canned visualizations that are excellent. In particular, visit Gapminder World which allows you to play with a wide range of world population data all they way back to 1800 embedded in a full browser screen. The graph ties nicely into a map as well to see the spatial relationships.
In case you are wondering if you can create your own moving bubble graphs with your data, yes you can. The renamed Gapminder is a now a Google Gadget called Motion Chart that anyone can use. The TED talks and other info available right on Gapminder's homepage. This webapp is very powerful for visualizing your data and a great tool to have in your digital toolbox.