Tara Smith's The Importance of the Subject in Objective Value: Distinguishing Objective from Intrinsic Value is a thorough review of the crucial distinction that Ayn Rand makes between the her concept of objectivity, which argues for a relational view of concepts, including moral concepts, and what she calls "intrinsicism," which is in fact what many people assume objectivity to consist of, but is in fact a failed attempt to divorce the subject from the object which ultimately and inevitably collapses into subjectivism.
Darryl F. Wright's Evaluative Concepts and Objective Values: Rand on Moral Objectivity attacks a related aspect of the same question. He discusses in some detail the underlying Objectivist epistemology and defends it from some critics. He then proceeds to show that what exactly moral objectivity involves, including its link to the goal of self-preservation.
Tibor R. Machan's Why Moral Judgements can be Objective attempts demonstrate the Ayn Rand approach succeeds in providing an objective morality, or as he puts it "there seems to be nothing amiss in the Randian idea of objectivity in ethics." While the overall thrust of this essay is reasonable, and it is clear that Machan is sympathetic to Objectivism, I couldn't help noticing an unfortunate lack of commitment to the very ideas that Machan presents. For example, he concludes that
...it is most likely true that objectivity is possible in ethics, provided that knowledge is conceived in an essentially non-Platonist, non-idealist fashion and provided that “objective” is not taken to mean that moral values are intrinsic.It seems to me that Machan concedes too much to rather unworthy critics with the above statement.
Finally, I thought that Douglas B. Rasmussen's The Importance of Metaphysical Realism For Ethical Knowledge was probably the most interesting essay I read. Rasmussen discusses the views of philopher Hilary Putnam in some detail. Putnam claims that moral objectivity is possible despite denying any underlying metaphysical reality in way similar to Kant. Rasmussen carefully lays out Putnam's sometimes varying positions on the matter and shows conclusively that Putnam's attempt to present an objective morality without an objective reality fails. What was most fascinating about this particular essay is that the political implications of Putnam's views are also discussed. Thus the essay serves as a good illustration of the power of basic philosophy, including metaphysics and epistemology, to influence both ethical and political ideas.