It's funny...most of the books and essays I would have thought to recommend are conspicuously absent from your list. Specifically, those which require one to refine what it means to be a libertarian, and how libertarianism differs from other views, aren't really there. Glad to see that at least Nozick made the cut! But with that in mind, I'll offer my own reading list:
John Stuart Mill: On Liberty
Ludwig von Mises: The Anti-Capitalistic Mentality
John Locke: On Civil Government (the "second treatise")
Robert Nozick: Anarchy, State, and Utopia
Judith Jarvis Thomson: Rights, Restitution, & Risk
Joel Feinberg: Social Philosophy
Freidrich August von Hayek: "The Use of Knowledge in Society"
Henry Hazlitt: Economics in One Lesson
Ronald Coase: "The Problem of Social Cost"
Garrett Hardin: "The Tragedy of the Commons"
Dan Hausman and Michael McPherson: Economic Analysis and Moral Philosophy
Lionel Robbins: "Interpersonal Comparisons of Utility: A Comment"
John Harsanyi: "Does Reason Tell Us What Moral Code to Follow and, Indeed, to Follow Any Moral Code at All?"
G. A. Cohen: Self-Ownership, Freedom, and Equality
Michael Otsuka: Libertarianism Without Inequality
Becky Mansfield: "Privatization: Property and the Remaking of Nature-Society Relations"
Randall Holcombe: "Common Property in Anarcho-Capitalism"
Roy Cordato: "Market-Based Environmentalism and the Free Market: They're Not the Same"
Peter Hill: "Market-Based Environmentalism and the Free Market: Substitutes or Compliments?"
Mark Pennington: "Liberty, Markets, and Environmental Values: A Hayekian Defense of Free-Market Environmentalism"
David Roodman: "Another Take on Free-Market Environmentalism: A Friendly Critique"
Walter Block (ed): Economics and the Environment: A Reconciliation (especially Murray Rothbard's "Law, Property Rights, and Air Pollution")
Gerald Sauer: "Imposed Risk Controversies: A Critical Analysis"
Douglas Lackey: "Taking Risk Seriously"
Kristian Skagen Ekeli: "Environmental Risk, Uncertainty, and Intergenerational Ethics"
Kenneth Templeton, Jr. (ed): The Politicization of Society
William Graham Sumner: What Social Classes Owe to Each Other
David Beito, Peter Gordon, and Alexander Tabarrok (eds): The Voluntary City: Choice, Community, and Civil Society
The order of these selections was intentional, and I think anyone who hasn't read these books and essays would benefit immensely from reading all of them. They represent a broad array of different viewpoints; not all of them are even written by libertarians. But the ideas contained in each of them have been critical to my understanding libertarianism as a philosophical position, and not just as an opinion. I don't agree with most of them, but they've all helped me understand my own views a lot better. I'm sure there are a lot of things that absolutely should be on that list, but aren't, and for that I apologize; I'm only 21. Most obviously, Rawls isn't on the list because I haven't actually read his books (
A Theory of Justice and
Justice as Fairness: A Restatement, specifically, would probably be on the list if I had read them). But the things on this list are, I think, the most important libertarian-themed books I've ever read (believe it or not, most of what I've read didn't make the list), and hopefully that counts for something.
http://libertarian-left.blogspot.com/