The Federal Government Shutdown has affected the following institutions. These are institutions that serve the American people and citizens of the world by connecting people to valuable information and resources. I will update this list as more websites and institutions are forced to shutdown due to a lack of funding. Please feel free to comment with sites that I have missed, as I am sure there are many.
Library of Congress: http://www.loc.gov/home2/shutdown-message.html
The Smithsonian: http://www.si.edu/
National Archives: http://www.archives.gov/
US Census Bureau (and American Fact Finder): http://outage.census.gov/closed.html
Government Printing Office: http://www.gpo.gov/fdsys/
Department of Justice Web Portal: http://www.justice.gov/