Congressional Quarterly Almanac Plus
Yearly publication which provides information on every major piece of legislation to pass through Congress from that particular year. Includes both bills that became laws and ones that did not.
The U.S. Congress Votes Database
Contains "every vote in the U.S. Congress since 1991." Browse by Congress or by member of Congress.
Safire's Political Dictionary by 
Dictionary of American Government and Politics by 
Encyclopedia of the American Constitution
Four-volume encyclopedia providing definitions of terms, articles on constitutional history and political issues, biographies of important people,
information on court cases, and much more
The Palgrave Encyclopedia of Interest Groups, Lobbying and Public Affairs by 
Political Encyclopedia of U. S. States and Regions by 
International Encyclopedia of Civil Society by 
The Princeton Encyclopedia of American Political History. (Two Volume Set) by 
The Statesman's Yearbook 2013 by
Yearly publication detailing information on international organizations and the countries of the world. Country information includes a map, capital, key historical events, territory and population, social statistics, government, elections, current administration, economy, culture, and more.
Handbook of Politics: State and Society in Global Perspective by