Marxists.org = free source of translated writings by many major figures. Woot!

I'll also pimp an author who had a major influence on me: Schweickart: After Capitalism. Short, sweet, clearly written - yes, market socialism, which I understand is a controversial theory, but he's really good at explanation and he is of your clan: he did his Ph.D. in mathematics first, then jumped ship to do a second one (o.0) in philosophy at Ohio State University. :-D