Means tested welfare programs (excludes SS/medicare) cost the FedGov over $1 trillion dollars in 2011, making this the government's largest expenditure.
And this is just Fed programs.
Govt spent $1.028 trillion on welfare in FY 2011 | The Daily Caller
The government spent approximately $1.03 trillion on 83 means-tested federal welfare programs in fiscal year 2011 alone — a price tag that makes welfare that year the government’s largest expenditure, according to new data released by the Republican side of the Senate Budget Committee.
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The data excludes spending on Social Security, Medicare, means-tested health care for veterans without service-connected disabilities, and the means-tested veterans pension program.
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CRS reports that food assistance programs — the third largest welfare category behind health and cash assistance — experienced the greatest increase in spending, with 71 percent more spending in 2011 than in 2008. The agency explained that this spending increase was largely due to the growth in the Supplemental Nutrition Assistance Program, or food stamps.