This list is more or less a random collection of references to unpublished manuscripts that I have come across.

A Plea for Mechanisms
Unpublished Manuscript

Forces and Relations of Production
Unpublished (mentioned in G. A. Cohen, Functional Explanation, p. 35)

Is the concept of contradiction useful in the social sciences?
Paper presented to the Fourth Bergen Seminar on Mathematical Sociology

Freedom and Power
Unpublished mimeo, Oslo (University of Oslo?)

When Ignorance is Bliss
Unpublished manuscript, Department of Political Science, University of Chicago

Arguing and Bargaining
Unpublished manuscript, Department of Political Science, University of Chicago

Arguing and bargaining in two constituent assemblies
The Storrs Lectures, Yale Law School

Optmism and pessimism in the discussion of the standard of living during the Industrial Revolution in Britain
Report to the XIV International Congress of the Historical Sciences, San Francisco

Ulysses and meta-rationality
Paper presented to the ECPR Workshop on Political Theory, Louvain

Beyond gradient climbing
Paper presented to the Fourth International Congress of the Study of Human Development

Production et reproduction: Essai sur Marx Thesis (Docteur ès lettres et sciences sociales from the University of Paris V, 1972.)

Prise de conscience dans la Phénoménologie de l'Esprit de Hegel
(Self-Consciousness in Hegel's Phenomenologyof Mind)
Thesis (Mag.art.(philosophy) from the University of Oslo, 1966)