Via several blogs, I've come across this interactive graphic entitled "Budget Puzzle" from the NYT. It's somewhat buggy (sometimes allowing both mutually exclusive items to be selected) but it is also much more comprehensible than the other budget calculators I've played with. Most others only give results for the next year, but the NYT version shows results at two different points in the future, which is much more useful. My solution used early withdrawals from our land wars in Asia, efforts to slow the growth rate of medical expenses, an end to the giant tax holiday the rich have enjoyed over the past 7-9 years, and new taxes on carbon and the banksters.
ETA: Klein has links to some other budget calculators.