I've pretty much stopped being able to hear or understand the kind of numbers the federal government is trafficking in these days. And those "if you stacked one dollar bills they would reach Jupiter!" explanations simply reinforce the concept which I already grasp: The numbers are very large.
But here's an interesting way to think about trillions:
A trillion dollars is about the total amount collected in income taxes by the U.S. federal government in fiscal year 2006—$1.04 trillion, if you're curious to use the exact number. That gives me a simple rule of thumb for personalizing these numbers. If I want to know what an additional trillion dollars in government borrowing or spending will mean for me, I just imagine what it would be like to pay twice as much in federal income taxes for one year.
So, for example, with the President's proposed budget calling for deficits of $1.75 trillion for 2009 and an additional $1.17 trillion for 2010, after 3 years of paying twice as much as I paid in 2006, I'd have about paid off my share of the bill for the first two years of the proposal.
Don't push this too hard, it's not a strict reckoning of accounts due and no one expects that the government will be asking individuals to cut checks next year to balance the budget. But do take a minute to ponder.