The Top500Minder is an interactive visualize of the Top500 lists going back to 1993 that lets you plot HPC growth against nations per-capita and GDP, showing the growth. Of course, right now everyone is plotting the differences between US and China. Shown above is the Flops Per $GDP for the US and China, showing how China has nearly caught up.
The visualizations are very similar to the popular Hans Rosling moving charts, flash and web based.
I’ve got a Tableau Public viz for this one too: http://public.tableausoftware.com/views/Top500/TFLOPsGDPandPopulation
-Robert