Yesterday, the U.S. Government Printing Office announced the release of the President's Budget of the United States Government for Fiscal Year 2014. The Goodson Law Library's print copy has not yet arrived, but users can read and search the online version at FDsys or the Office of Management and Budget. And there's even an app version for mobile devices!
For news and information about the President's budget proposal as well as the competing version in the House of Representatives, visit the Center for Effective Government (formerly known as OMB Watch). This nonprofit research center provides analysis of budget proposals. CQ Weekly, a subscription database available to the Duke University community, contains regular reports on budget-related actions in Congress.
Historical budgets can be found through FDsys back to 1996 and through the Federal Reserve back to 1926. The Goodson Law Library also maintains a historical print collection of the federal budget at Documents PrEx 2.8. For assistance with locating current or past federal budgets, be sure to Ask a Librarian.