On August 31, the U.S. Census Bureau released a report which found that federal domestic spending obligations increased 16 percent to $3.2 trillion in 2009, the largest annual increase since the bureau began compiling federal spending data in 1983.  The Census Bureau suggests that much of that increase is attributable to spending under the American Recovery and Reinvestment Act (ARRA).  The report also notes that Medicare, Medicaid, and Social Security comprised 45.7 percent of all federal domestic spending, or $1.5 trillion. 

From the report:

The Consolidated Federal Funds Report (CFFR) is a presentation of data on federal government expenditures or obligations in state, county, and subcounty areas of the United States, including the District of Columbia and U.S. Outlying Areas. It is collected under the authority of Title 13 of the U.S. Code and contains statistics on the geographic distribution of federal program ependitures, using data submitted by federal departments and agencies. These data have been consolidated and tabulated in a standard format by the U.S. Census Bureau, under the auspices of the U.S. Office of Management and Budget, for presentation in publications and electronic form.

Full Report: Consolidated Federal Funds Report for Fiscal Year 2009 (PDF | 1.25 MB) 

U.S. Census Bureau. (2010). Consolidated federal funds report for fiscal year 2009.