Even though I don't always agree with him on all moral issues, I think Sam Harris makes the best case for a secular objective morality in The Moral Landscape.
I haven't read "The Moral Landscape." How does Harris kick things off? I can see how by using particular ethical models you can come to consistent moral positions, but these still require that you start from a subjective axiom: e.g. being alive is better than not being alive.
I guess I need to know how objective is defined first. Does Harris propose that his objective morality would be as valid for aliens? If it doesn't apply everywhere and everywhen for everyone, and relies on external inputs to get moving, I don't think a morality is objective.
The magic 8 ball approach is as close as I've seen anyone come to defining an objective moral framework, but it isn't one I would subscribe to and it serves to re-illustrate the difference between morals and ethics.