I'd include Francis Fukuyama on the conservative side.

Leo Strauss (and any Straussian like Allan Bloom or Harry Jaffa), Robert George, Charles Murray, Michael Novak, Eric Voegelin, Tocqueville, John Adams, James Burnham, Disraeli, Robert Bork, Richard Weaver, and Leon Kass

The most frequently referenced name during the Federalist - Antifederalists debate on the U.S. Constritution was Montesquieu.

 On the liberal/radical side - perhaps William Appleman Williams and Charles Beard? 

I would also add James Burnham, Jose Ortega y Gasset, and Karl Popper. Burnham was a leftist turned conservative, Ortega was a European semi-traditionalist conservative, and Popper was a strong advocate of liberty as opposed to social engineering.  

Add also for a tradtionalist intellectual perpsective  Jacques Barzun.

Hobbes, of course, and Locke.

Scottish enlightenment figures in addtion to Smith, such as Dugald Stuart (Stewart)  and David Hume. 

I think it's important to emphasize the classical liberal tradition has become an important bedrock of conservative thought today.

Today's conservatism is not the conservatism of Taine.

I believe Thomas Sowell should be on this list. Not because of the incalculable good he has done in explaining basic economics to the average citizen, but rather due to his groundbreaking work in A Conflict of Visions. This book helps to present the whole framework for this very discussion.

Joseph de Maistre should be added to the conservative side of the equation. Vasilii Rozanov, as well, although I'm unsure if any of his works have been translated into English.

Furthermore, you can pile the entire pomo canon onto the radical scrap heap. Lyotard, Saussure, Barthes, Foucault, Derrida, Deleuze, Irigaray, DeCerteau, Hayden White, Rorty.

Then there's the Frankfurt School, very relevant to the modern New Left's cultural agenda, which, in addition to Marcuse, includes Walter Benjamin, Max Horkheimer, and Theodor Adorno.

Habermas has tacked slightly rightward of late, and would probably now belong in the liberal camp.

Raymond Williams was a hard-shell Leftist.

Add the various great intellectual historians below who span both academic disciplines and the poltiical spectrum. Intellectual history is now the most forbidden discipline in academe because ot its "elitism:"

Jacob Burckhardt; Frederic Maitland; Arthur O. Lovejoy; Carl Becker; Friedrich Meinecke; Ernst Troeltsch; Johan Huizinga; Elie Halevy; Paul Hazard; Frederick Teggart; George B. Sansom; Erich Auerbach; C.N. Cochrane; C.S. Lewis; Ernst Curtius; Ernst Kantorowicz; Harry Wolfson; Carle Zimmerman; Gershom Scholem; Gustave von Grunebaum; Hans Baron; Hubert Jedin; Gerhard Ladner; Arthur M. Wilson; Joseph Needham; Paul Oskar Kristeller; Felix Gilbert; Perry Miller; Arnaldo Momigliano; E.H. Gombrich; Maurice Mandelbaum; David Daube;  Robert Nisbet; Philippe Aries; Franco Venturi; Owen Chadwick; Henry Chadwick; Philip Curtin; Kenneth Lynn; Masao Maruyama J.G.A. Pocock; Elie Kedourie; John T. Noonan;  Leszek Kolakowski; H.E.J. Cowdrey; Eric Cochrane; John Bossy; Karl Morrison; Ernst Gellner; Bernard McGinn; David Brading; Hiram Caton; Bruce Kuklick; Benjamin Elman; Charles A. Hale; Mark Noll; and Allen Guelzo.

 I don't have much interest in these political issues but they come up in my teaching about human diversity all the time.  I would like to read the top 8, 2 from each category, when the list is complete.  I certainly don't want to read 40!  Good Luck.

Thanks for the recommendations everyone! We are adding each name to our list of nominated authors. A quick reminder of our guidelines - we are looking for post-1750 books that:

(A) unambiguously represent different strands of political theory,

(B) are widely recognized, and

(C) are plausible material for undergraduate courses.

Keep the suggestions coming!

I'd include Frederic Bastiat's The Law and perhaps something written by Charles Murray. Both would fall into the libertarian canon, I think.

On the conservative side:  The U.S. Constitution.  The Declaration of Independence.   Essays on Political Economy by M. Frederic Bastiat.   Extraordinary Popular Delusion and the Madness of Crowds by Charles Mackay.  The Forgotten Man by Amity Shlaes.  Do the Right Thing: The People's Economist Speaks by Walter E. Williams.  Liberty and Tyranny by Mark Levin.

On the liberal side:  Class Matters by Bill Keller, or anything by Al Gore, William Ayers, or Michael Moore.

I'm amazed that the anarcho-communist Noam Chomsky has not been mentioned. Other more traditional anarchists are Petr Kropotkin and Mikhail Bakunin.

Louis du Bonald, a French conservative writing after Le Revolution.  His book "On Divorce" is an excellent examination of the intersection of law, culture, religion, and politics regarding marriage and divorce, utterly and completely untainted by feminism.

G.K. Chesterton - highly readable, examines the intersection of politics and morality, responding to the early Progressive/Left strains at the dawn of the 20th century. - Conservative

Amitai Etzioni - Communitarian

First, let me recommend that whatever books are chosen, care should be taken to ensure that they not represent caricatures of particular views. 

Second, its not clear whether you're looking for books to introduce ideas to students, or for books that seriously engage the subject matter.  Rand's work might be fine to raise certain topics for discussion, but will likely not suffice for serious inquiry. 

As far as authors, I think Ronald Dworkin should be on the list.

Many excellent suggestions. There are a few important names I don't think I saw here....though if I'm wrong, please accept my apologies! On the conservative side---Robert Nesbit, Irving Babbitt, John Adams, Jacques Ellul.  On the other side---Antonio Gramsci, Richard Rorty.

Two books that are classics for their elucidation of scientific facts that are anathema to left-wing ideas are:

E.O. Wilson, On Human Nature, Harvard Press (1978).  Refutes the idea that all human relations are "social constructs."  Founded the field of evolutionary biology.

Julian Simon, The Ultimate Resource 2, Princeton Press (1996).  Refutes Malthus, Ehrlich, the population control movement, the concept of resource limits, and the vast majority of environmental extremism. 

Both books are profoundly important for biology, social sciences and political philosophy and should be included in an intellectually diverse curriculum.

I think Benedetto Croce could be counted a conservative by contemporary standards.

David Horowitz, Roger Kimball and Sidney Hook, on the conservative side, of course.

names that I believe haven’t been mentioned:

Irving Kristol
Richard John Neuhaus
Christopher Dawson
John Henry Newman
Matthew Arnold
Daniel P. Moynihan
George Gilder
Pope Leo XIII
Romano Guardini (Letters from Lake Como)
Rachel Carson
John Polanyi
Lincoln
Churchill
Pope John Paul II

Einstein -- a little unusual
Yogi Berra -- no explanation needed!

Walter Bagehott and Roger Scruton on the conservative side. If you want to include literary figures then you can't omit Robert Frost, T. S. Eliot, Wallace Stevens, Osip Mandelshtam, Fyodor Dostoevsky, Boris Pasternak and Aleksandr Solzhenitsyn, conservatives all of them.

Walter Lippmann

Authors on the left/radical side: (these aren't of the current liberal tradition, they are leftists) and a representative work

Noam Chomsky (he is actually an Anarcho-Syndicalist, not a communist. He explains in his literature explicitly why he is not a Marxist/Leninist/Stalinist): Objectivity and Liberal Scholarship

Edward Said (literary criticism, political activist): Orientalism

Howard Zinn (historian, teacher, 1960s Civil rights activist): The Politics of History

Robert W McChesney: Rich Media, Poor Democracy

Samuel Clemens: Any turn of the century political work, his views were highly radical, including support for the Russian revolution, anti-colonialist sentiment, and anti-racism.

Peter Kropotkin: Mutual Aid

Alexander Cockburn: The Golden Age is in us

Classical liberal authors/journalists

Richard Hofstadter: The American Political Tradition: and the men who made it

Walter Lippmann: Public Opinion

John Dewey: Democracy and Education

I.F. Stone: The Truman Era

Also, Perry Anderson does an excellent summarization of political views called Spectrum: from right to left in the world of ideas.

Definitely add Vaclav Klaus, with Blue Planet in Green Shackles as his major work.  I suppose that nowadays we'd call him conservative, though he thinks he's a classical liberal.

Reaching a little farther into Czech past, how about "The Grand Old Man of Europe," namely Thomas Garrigue Masaryk, and his books such as The Making of a State and Modern Man and Religion?