Nontheistic sources of morality?

James Fitzpatrick at Catholic Exchange has a few words to say about the conservative Christian habit of praising God's mercy every time something good happens and every time something bad happens that could have been worse, but not blaming God for when things are worse than they could have been. The point was more about how the religiously inclined tend to rely on an external, ineffable, personal source for the morality of the world, while atheists don't. I'm not really being representative here but I needed to provide a little context for my own point.

It's often said that without a transcendent and absolute moral reference, then the only alternative is relativism. Broadly speaking, I agree, but on a case by case basis it's possible to resist the grayness that comes from trying to reconcile disparate moral codes (some of the time, perhaps by declining to reconcile at all) on the grounds that if we all have the same moral authority and all our codes aren't wrong then there must be some unifying principle behind all the codes being in some way right. It's not news that someone can recognize, without being told, that it's good to be excellent to each other and it's better to couple excellence with fairness, in all those specific ways like sharing, not stealing or killing, and everything else. From the article:

It is just that they "look elsewhere for a sense of order, valuing the rule of law for its transparency to all rational minds and debating Supreme Court decisions without reverting to mystical precepts of 'natural law.'" [Heather MacDonald] argues that "[s]keptical conservatives do not look into the abyss when they make their moral choices. Their moral sense is as secure as a believer's. They do not need God or the Christian Bible to discover the golden rule and see themselves in others."

I dunno about this "look into the abyss" line. Maybe it's a Nietzsche reference, although any theist will tell you there's a difference between contemplating the divine and contemplating the nil, whether or not an atheist will look for himself to check. I don't expect most atheists to bother with Catholic-steeped philosophy, either, but I do hope that MacDonald isn't on the "Call us Brights! It's more accurate less dour!" bandwagon. Independently discovering the golden rule and seeing yourself in others is a classic example of natural law. Isn't that much self-evident?