For more see the Government Information portal at Columbia. If you are unfamiliar with how the American Government is set up (it's confusing!) please consult this fabulous set of resources from USA.gov.
Department of Energy: The Department of Energy has four distinct missions: Energy, Defense, Cleanup and Waste Management, and Science, Technology and the National Labs.
DOE Information Bridge: This web site includes the full-text and bibliographic records of DOE-sponsored report literature produced by the DOE and DOE contractor research and development community.
Assistant Secretary for Planning and Evaluation: The principal advisor to the Secretary of the U.S. Department of Health and Human Services on policy development, and is responsible for major activities in policy coordination, legislation development, strategic planning, policy research, evaluation, and economic analysis.
Centers for Medicare and Medicaid Services (CMS) administers the Medicare and Medicaid programs, which provide health care to America's aged and indigent populations. CMS also administers the new Children's Health Insurance Program through approved state plans that cover more than 2.2 million children.
Department of State: The Department of State is the primary source of foreign affairs information for the U.S. Government and is responsible for implementing the President's foreign policies.
Don't forget that the State Department has had many versions of their website that can be accessed at their web-archive.
Background Notes - U.S. Department of State: Brief profiles of most countries of the world. Includes information on government type and structure, names of major government officials, and an overview of foreign relations.
Agency for Toxic Substances and Disease Registry (ATSDR): ATSDR implements the health-related sections of laws that protect the public from hazardous wastes and environmental spills of hazardous substances. This site connects to various databases and includes lists of Superfund sites.
Climate Diagnostics Center: The mission of the Climate Diagnostics Center (CDC) is to identify the nature and causes for climate variations on time scales ranging from a month to centuries. It is a joint project of CIRES (Cooperative Institute for Research in Environmental Sciences) and NOAA (see below).
Coordinates U.S. international energy policy related to commodities, including energy supply, and U.S. participation in the International Energy Agency; monitors cooperative multilateral and bilateral agreements related to energy; coordinates energy-related aspects of U.S. relations with other countries.