http://www.firstgov.gov
A Database of Federal services and links to every federal government site

http://www.fda.gov
United States Food and Drug Administration, regulations and information on food and drugs

http://www.uspto.gov
US Patent and Trademark Office, information on patents and trademarks

http://www.customs.gov
US Customs Service, information on regulations regarding importing and exporting and information for travelers

http://www.irs.gov
Internal Revenue Service, tax forms and Information on taxes

http://www.census.gov
US Census Bureau, statistics and market information

http://www.access.gpo.gov
Government Printing Office, information on all government publications

State Government

http://www.firstgov.gov/Agencies/State_and_Territories.shtml
A gateway to all the 50 states official webpages

http://www.case-europe.com
Council of American States in Europe. Professional assistance to European firms interested in establishing or expanding a business in the USA, represents American manufacturers and a good source of U.S. manufactured products.