Communist Manifesto - Karl Marx & Engels
Synopsis of Marx's Capital - Engels
Anti-Duehring - Engels
Socialist: Utopian and Scientific - Engels
Dialectics of Nature - Engels
Origin of Family, Private Property, and the State - Engels
A collection of Malcolm X excerpts -
What is to be Done? Burning Questions of our Movement - Lenin
Imperialism, the Highest State of Capitalism - Lenin
State and Revolution - Lenin
Permanent Revolution - Trotsky
What is Dialectical Materialism? - Rob Sewell
There's many more, but there's some off the top of my head.