"The tragic events of September 11, 2001, have brought increased Congressional and public interest in federal spending for homeland security. Funding for those activities is split among 200 different appropriation accounts within the federal budget and involves many different functional areas of the government. Furthermore, most of the funding resides within accounts that primarily finance programs that are not classified as homeland security activities. That accounting arrangement makes it difficult for budget analysts to distinguish and track homeland security spending. Most of the current data on funding for homeland security are provided in annual reports to the Congress by the Administration's Office of Management and Budget (OMB). Largely on the basis of those reports, the Congressional Budget Office (CBO) estimates that federal resources dedicated to homeland security activities will total about $41 billion in 2004--roughly double the amount allotted to those activities before September 11. For 2005, the Administration has proposed increasing homeland security funding to $47 billion, or about 14 percent above the current level."
Congressional Budget Office: http://www.cbo.gov