Some links of interest to engineers:
American Association of State Highway and Transportation Officials (AASHTO)
American Forest and Paper Association
American Institute of Steel Construction (AISC)
American Institute of Timber Construction
American Iron and Steel Institute (AISI)
American Society of Civil Engineers
Cold Regions Research and Engineering Laboratory (CRREL)
Environmental Protection Agency (EPA)
Federal Emergency Management Agency (FEMA)
Federal Energy Management Program
Federal Geographic Data Committee
Federal Highway Administration (FHWA)
General Services Administration (GSA)
Guide to Wood Design Information
National Aeronautics and Space Administration
National Interagency Fire Center
National Register of Historic Places
Natural Resources Conservation Service (NRCS)
Occupational Safety and Health Administration (OSHA)
Portland Cement Association (PCA)
United States Geological Survey (USGS)
United States Metric Association (USMA)
Wood in Transportation National Information Center