Base, Meet Superstructure
Marxism.org's philosophy resource is a splendid collection of philosophical texts from Descartes & Hobbes to Adorno, Sartre and Rorty. Essential reading! First on my reading list: the introduction to Consequences of Pragmatism by Richard Rorty, which I might just write an entry about sometime soon.
Actually, Marxists.org itself is an amazing resource, filled with original texts from all over some several canons. A bit heavy on the Engels, Hegel, Lenin, Stalin, Mao and Trotsky thing. But then, it's Marxists.org. What do you expect? They have texts by Leibniz too, and he was just completely goofy.