Foundational texts on socialism and communism. There's some overlap with the 'anarchism' index. Come get the OG red pill.
Kropotkin, Pyotr: The Conquest of Bread
Kropotkin, Pyotr: Mutual Aid: A Factor of Evolution
Engels, Friedrich: The Condition of the Working-Class in England in 1844
Marx, Karl and Engels, Friedrich: The Communist Manifesto
Proudhon, Pierre-Joseph: What is Property? An Inquiry into the Principle of Right and of Government
Wilde, Oscar: The Soul of Man Under Socialism
Unfortunately, Project Gutenberg does not provide an English-language text of Karl Marx's "Capital". Instead, readers who wish to read it must go instead to marxists.org on the Web.
Capital, Volume I: The Process of Production of Capital
Capital, Volume II: The Process of Circulation of Capital
Capital, Volume III: The Process of Capitalist Production as a Whole