In 1949, Leo Strauss, the German-Jewish emigré, landed at The University of Chicago, where he spent decades teaching and writing on political philosophy, especially the political thought of the Ancients. Strauss' thinking skewed conservative, and if he was sometimes controversial while alive, he has become only more so in death (1973). Nowadays he's considered rightly or wrongly the "intellectual godfather of the neo-conservative political movement," if not an "intellectual force behind the Bush administration's plan to invade Iraq." Although Strauss commented occasionally on contemporary politics (Harper's has more on that), he spent most of his time working through major philosophical texts, and through his commentaries, developing his own philosophical positions, which were generally hostile to the Enlightenment project and modern individualism/liberalism.
Strauss was unquestionably an influential figure even if he still divides us, and now, courtesy of U. Chicago, you can listen to 15 of his philosophy seminars online. They were recorded between 1959 and 1973, and some representative titles include Montesquieu’s The Spirit of the Laws (a course that Paul Wolfowitz took during the early 70s), Nietzsche's Beyond Good and Evil, Hobbes' Leviathan, and Hegel's The Philosophy of History.