The White House, Public Residence of the President
The American Presidency Project: a non-profit and non-partisan source of presidential documents
American Presidents: Life Portraits: C-SPAN's series profiling past presidents
Center for the Study of the Presidency: CSPC works with leading experts on presidential and congressional history to provide engaging case studies on political leadership, legislative compromise, and national strategy
Presidential Directives and Where to Find Them: from the Library of Congress, links to presidential directives. These directives go by different names and are are signed or authorized by the President. They are issued by the National Security Council
The White House Historical Association: a nonprofit institution whose purpose is to enhance the understanding, appreciation and enjoyment of the White House.