U.S. Patent Office 

Occupational Safety and Health Administration (OSHA)
Information and resources to aid compliance with federal health and safety regulations

Environmental Protection Agency  
Federal regulations affecting environmental and natural resources, waste disposal, air quality, water, obtain regulatory updates, find regional staff and offices, local assistance programs, get news, etc

The Department of Labor  
Comply with federal labor regulations, access to online library and more

U.S. Citizenship and Immigration Services
Federal immigration regulations, forms, review filing fees, instruction for employee hiring/verification and reporting requirements

Federal Register  
The official daily publication for Rules, Proposed Rules, and Notices of Federal agencies and organizations, as well as Executive Orders and other Presidential Documents.

Thomas - Legislative Information on the Internet  
A complete online searchable database of almost all activities of the US Congress. A directive of the 104th Congress to "make Federal legislative information freely available to the Internet public" created it.

Department of Commerce - International Trade Administration  
A comprehensive resource for information on all U.S. Federal Government export assistance programs