The subject suggested in the title is so broad as to make it rather difficult to decide what boundaries to draw around the study of various resources available to the historian or other social scientist who sets out to study labor history, the social history of Italian workers and peasants, and the political and intellectual history of socialism and other radical movements. Keeping in mind that the following discussion is not intended to be exhaustive, but rather an indication of the necessary starting point to begin an investigation is probably the best way to understand this note.