While I've not had time to play on the World Bank Datavisualizer (HT to Chartporn), I have played on the Gapminder site and they appear to be similar. In both cases, I find the visualizations fascinating and frequently very compelling. (You might want to start with the Teacher Tab on Gapminder, but poke around.) You might want to consider either or both of these for use with your classes.
What do you think?