The Weekly Standard says:
...roughly $2.3 trillion of the $2.5 trillion in savings from the Republican Study Committee's Spending Reduction Act would come from cutting non-defense discretionary spending to 2006 and freezing that spending through 2021.
Where does the rest of the money come from? The RSC wants to cut remaining stimulus funds, eliminate federal control of Fannie Mae and Freddie Mac, and eliminate automatic pay increases for federal employees for five years and reduce the federal workforce by 15 percent through attrition. The RSC has also proposed eliminating or cutting back more than 100 programs.
The list of programs is definitely worth reading. You'll probably find one or two of your favorites on the list including arts, Amtrak, and international aid.