I found this sweet website while doing research for my ongoing series on internation power trends (introduced here. It's got a boatload of statistics and allows you to create your own graphs. I'll be using it plenty in my article.
To whet your appetite, however, consider this (Note that it refers to external [i.e. foreign-owned] debt). Many people bitch about how large our national debt is and how scary it is that we owe so much to foreigners, and in absolute terms it is scary (~800 billion buckaroos). BUT in per capita terms it suddenly doesn't look so bad. The U.S. is #25, with countries like Australia, Sweden and Denmark in front of us. It's a neat new toy. (Yes I know I'm a nerd)