FOREIGN TRADE is the official source for U.S. export and import statistics and responsible for issuing regulations governing the reporting of all export shipments from the United States.
United States Census Bureau: Classifications of products, countries, customs districts.
U.S. Department of Commerce/International Trade Administration
United States Free Trade Agreements with Foreign Countries
State Export Data by State
U.S. Trade Laws
The World Bank: Merchandise Trade (% of GDP)