The first two sources probably present the most respected coverage of national politics.

CQ Weekly. Congressional Quarterly.

National Journal. National Journal.
Related publications include National Journal Daily and National Journal Hotline.

C-Span. C-Span.
Economist.com. Economist Newspaper Ltd. (Link to U.S. coverage.)
The Hill. The Hill.
Politico. Capitol News Company.
Real Clear Politics. Compilation site.
Roll Call.   Economist Group.
Washington Wire. Wall Street Journal.
Sabato's Crystal Ball.  University of Virginia.
ForeignPolicy.com. Slate Group.

Here are the politics sections of the New York Times and Washington Post.

These resources enable you to browse chronologically, examining issues and events in particular years or presidential administrations.

Congress and the Nation. Congressional Quarterly.

Quadrennial overviews of national politics, 1945-2008.

Congressional Quarterly Almanac. Congressional Quarterly.
In printed form only:  Reference collection: REF JK 1.C7

Annual overviews of national politics.

Historic Documents. Congressional Quarterly.

From 1972 through 2010.