Well, Archbishop Tutu has spoken (and was acknowledged by the Episcopal Cafe) but still from progressive American Christians, little else.
Teju Cole in The New Yorker writes:
We now have firsthand testimony from the pilots who remotely operate the drones, many of whom have suffered post-traumatic stress reactions to the work. There is also the testimony of the survivors of drone attacks: heartbreaking stories of mistaken identity, grisly tales of sudden death from a machine in the sky. In one such story reported by The New York Times, the relatives of a pair of dead cousins said, “We found eyes, but there were no faces left.” The recently leaked Department of Justice white paper indicating guidelines for the President’s assassination of his fellow Americans has shone a spotlight on these “dirty wars” (as the journalist Jeremy Scahill rightly calls them in his documentary film and book of the same title). The plain fact is that our leaders have been killing at will.
In some ways, what’s most disturbing about the Obama white paper is not that it tried to set limits in order to ensure that the drone program was within the laws of war. Rather, what seems more worrisome is what it didn’t attempt to figure out, and which no one else seems to be addressing either: namely, whether conventional laws of war should still apply to America’s unconventional counterterrorism program, particularly now that it is over a decade old, and is seemingly morphing into an endless worldwide lethal manhunt. Drones per se are weapons, and they are not so much the problem as the parameters of the war in which they’re being used.
We may talk about the “drone war” and debate the drone memo, but we’re not really looking at the use of a specific technology. Instead, the “drone debate” is about policy, and how the United States chooses to attack its enemies in the War on Terror. Fancy as modern drones may be, it’s the policy that makes this kind of war new.
Preaching Grace on the Square 
By now, it should be apparent that the conflicts in which we and other powerful states have been engaged since the end of the Cold War all have been “dirty wars” in the sense that they seldom involve the armed forces of organized opposing states that are capable of command and control of force. The perpetrators of violence are more like pirates who attack the values and interests of whatever party they can, for a host of reasons having little to do with the protection of their homeland. In such a violent international society, it makes very little sense to talk of “laws of war,” which evolved to limit the destructiveness of conflict among more or less well established states. This reality presents serious moral dilemmas for leaders whose objectives are not only to protect their own citizens from harm but also to reduce the amount of chaos in the world.
Targeted assassinations are a reflection of the chaotic nature of current international political life — just as they were in medieval Italy or at other times when states had to contend with a variety of forms of terror. What it is reasonable to demand of our leaders is that they weigh the consequences of their actions carefully and that they be more scrupulous in the use of force at all levels. Invading other countries out of spite is far worse than attacking a site that is believed to harbor a pirate, though in a more perfect world one would not choose to do either.