SAC librarians have collected these very informative sources:
From the GOVDOCS listserve:
Here is a list of government websites that are completely offline or "dark":
USGS.gov
Bureau of Economic Analysis (bea.gov)
Business.gov
Census.gov
Copyright.gov
Data.gov
Disability.gov
ERIC (eric.ed.gov)
FCC.gov
FTC.gov
Library of Congress (loc.gov)
NASA.gov
National Park Service (nps.gov)
NIMH.gov
NIST.gov
NOAA.gov is offline but you can still get to weather.gov
NSF.gov
Nutrition.gov
USDA (usda.gov)