Here are few links to books that I think are important.  Some may be foundational or historical while others may be great books to explain topics in the current world.  I will change this list as often as I have a need to and I would hope that you find it useful.  Please feel free to comment on books that I should add.

Economics

Applied Economics: Thinking Beyond Stage One ~ Thomas Sowell

U.S. Government

The Federalist Papers
The Anti-Federalist Papers and the Constitutional Convention Debates
Common Sense, The Rights of Man and Other Essential Writings of Thomas Paine
American Cause Russell Kirk

Capitalism

Capitalism and Freedom ~ Milton Freedman
The Wealth of Nations: Books 1-3 ~ Adam Smith
The Wealth of Nations, Books IV-V ~ Adam Smith

Socialism

Capital: Volume 1: A Critique of Political Economy ~ Karl Marx
Capital : A Critique of Political Economy (Volume 2) ~ Karl Marx
Capital: A Critique of Political Economy, Vol. 3 ~ Karl Marx
The Communist Manifesto ~ Karl Marx