This infographic visually breaks down the US Federal Discretionary Budget for 2007 into smaller and smaller bubbles. The actual values are also included as text, but the size of the bubbles instantly gives you an understanding of how the different budget items compare.
An online version in Flash is also available at thebudgetgraph.com
Just to be clear, this only shows the Discretionary Budget which totals $938 Billion. The total budget is $2.8 Trillion. Notice the circle in the background (just barely visible at the top and bottom) showing the National Debt of $9.35 Trillion.
One older version is the 2004 Budget.