This page provides links to the Office of Management & Budget (OMB), Congressional Budget Office (CBO) and Government Accountability Office (GAO) websites. CBO and OMB are intimately involved in the development and analysis of the Federal and Defense budgets, and GAO is responsible for monitoring federal (and defense) expenditures.
Office of Management and Budget (OMB) is the central budgeting agency that prepares the budget that the President submits to Congress. On their site you will find the current "President's Budget," past budgets, access to documents that OMB routinely issues such as Bulletins, Circulars, and Memoranda, and legislative information related to the budget process, and more.
Congressional Budget Office (CBO) provides Congress with objective cost analyses to help with economic and budgetary decisions on the programs covered by the federal budget, including Defense, and the information and estimates required for the Congressional budget process.
Government Accountability Office (GAO) is a government agency that works for Congress investigating how the federal government spends taxpayer dollars. They produce numerous reports on topics related to the federal and defense budgets.