The first thing I would like to say, is that when you total up the myriad details of what constitutes welfare, you will find that we pay more than 12% of our total tax dollars to welfare programs. Welfare is not a single item. It is comprised of many programs such as food stamps, education, child care, medical care, etc.
We currently spent, $350 billion a year on 79 means-tested federal welfare programs. That's more than we spend on national defense. Theoretically, we could take that money and give $8,939 to every poor person in America, or $35,756 to a family of four.
We currently spend more than 4.4% of our gross domestic product on welfare programs. Including state and federal government, we are spending about 22 to 45% depending on whose figures you want to go with. The Republican, Democrat, or libertarians.
You can read more at the following site: http://www.heritage.org/Research/Welfare/Test030701b.cfm
Here is a nifty chart that will be helpful in putting things into perspective.