American Presidency Project
The American Presidency Project is particularly strong in primary sources with over 68,000 documents to date. There is also summary data about presidential elections, approval ratings, public appearances, executive brnch growth, and congressional activity. An audio and video archive is also included at this comprehensive and well-organized site.
This site, from the University of Virginia, has two sections. The Presidency in History contains detailed biographies of each of the 43 past and present Presidents and First Ladies; biographies of Cabinet members, staff, and advisers; timelines detailing significant events during each administration; and multimedia galleries to explore. The Presidency in Action delves into the function and responsibilities of the modern presidency. Here you will find detailed descriptions of the areas of presidential responsibility, updated organization charts, staff listings, and biographies of past and present staff and advisers.
This web site contains information on Congress and its members. There is a section where members of Congress are rated by various political interest groups on issues of importance to the organization.
Found via the White House web site, this page lists the current members of the President's cabinet
US House of Representatives
The official Internet home of the House of Representatives, including information on the representatives and current and past legislation.
This web site contains information on the Senate and its members. Contact information for all US Senators can be accessed at this site.
This is the official site of the office of the President of the United States. The web site of the vice president can also be found here.