Internal Revenue Service
Use this link to search for undelivered or unclaimed federal income tax refund checks owed to you by the federal government.

National Association of Unclaimed Property Administrators (NAUPA)
Use this link to search for Unclaimed Property in all 50 states.

U.S. Federal Savings Bonds
Use this link to search for any U.S. Savings Bonds that you may have lost or forgotten about.

U.S. Department of Housing and Urban Development
Use this link to search for undelivered or unclaimed HUD/FHA mortgage insurance refunds.