I think we covered something like this on the old board.....
Projected amounts of federal foreign aid for 2003 are likely to total around $13.6 billion. The top two are Health and Human Services ($502 billion) and the DoD ($358.2 billion) so if you're looking to cut some serious money it would be advantageous to streamline these two. The nearest challenger to these two is the Dept. of Agriculture ($72.8 billion).
But I guess every little bit helps, eh?
For all you fact nazis
http://www.whitehouse.gov/omb/budget/fy2004/budget.html
I should note....there is no "official" cost of the War in Iraq, but every budget estimate I've seen (CNN; National Review; CBO) is in the $100-$150 billion range. Of course, there won't be any official numbers until all the data is in (rebuilding cost; length of occupation, etc.) but all estimates point to a significant amount.