The United States of America is the nation with most debt by far in history. At the end of 2011, the debt of the US federal government reached 15 Trillion Dollars ($15,000,000,000,000). The common run of people rarely deals with more than hundreds of dollars. How can we imagine how much one million, one billion, or one trillion dollars represent? What if we represented these sums with stacks of $100 bills...
One Hundred Dollars $100 — Most counterfeited money denomination in the world. Keeps the world moving.
One Hundred Million Dollars $100,000,000 — Plenty to go around for everyone. Fits nicely on an ISO / Military standard sized pallet.
One Trllion Dollars $1,000,000,000,000 — When the U.S government speaks about a 1.7 trillion deficit this is the volumes of cash the U.S. Government borrowed in 2010 to run itself. Keep in mind it is double stacked pallets of $100 million dollars each, full of $100 dollar bills. You are going to need a lot of trucks to freight this around.
If you spent $1 million a day since Jesus was born, you would have not spent $1 trillion by now... but roughly $700 billion, the same amount the banks got during the bailout. Comparison of $1,000,000,000,000 dollars to a standard sized American football field and European football field.
15 Trillion Dollars $15,000,000,000,000 —This is what the US national debt toppled by Christmas 2011. The Statue of Liberty seems rather worried as the United States now owes more money than its yearly production (GDP).
114.5 Trillion Dollars $114,500,000,000,000. — US unfunded liabilities. To the right you can see the pillar of cold, hard, $100 bills that dwarfs the (now disappeared) World Trade Center and Empire State Building — both at one point world's tallest buildings. If you look carefully you can see the Statue of Liberty.
The 114.5 Trillion dollar super-skyscraper is the amount of money the U.S. Government knows it does not have to fully fund all its programs. Note: On the above 114.5T image the size of the base of the money pile is half a trillion, not 1T as on 15T image. The height is double. This was done to reflect the base of Empire State and WTC more closely. (source: demonocracy.info)
Of course, such a sky-scraper of paper money will never exist, since the debt is made up of money that does not exist, and inflates because of coumpound interest. Even if all the money in circulation was collected to pay the debt, one would not even pay back one percent of this debt.