Little know fact, the United States Air Force spends more now on Unmanned Ariel Vehicles (such as Predator Drones) than on traditional, piloted aircraft. Of course, UAV's do, in fact, have pilots. It's just that the pilots fly the vehicles remotely from bases. There are a lot of advantages of this besides lowering the risk in operations over hostile territory. Without the weight of pilot, human interface (cockpit), or the life-support/survival equipment associated with pilots, these airplanes can have incredible range and time-over-target. If pilots become tired, no problem, they just get up and another pair takes their place in the command centre! The current (declassified) record for a single Predator flight is 40 hours and 5 minutes (source).
The existence of the "RQ-170 Sentinel" has just been declassified. It looks like a smaller version of a B-2 Bomber: flying wing with no tail. Few details have been released, but the aircraft is obviously designed to minimize radar signature. It is believed that it does not carry weapons (but that assumption is really just based on the RQ designation declassified by the Air Force). Aviation Week says that it is probably a "tactical, operations-oriented platform and not a strategic intelligence-gathering design" (source). But a lot bloggers point out features of the design that suggest an internal weapons bay.
I have a great story, incidentally, that an USAF officer told me about a Predator giving operational support during the invasion of Iraq. I don't think it's a classified story, but I'm not going to share it online. Suffice it to say that these things are amazing. I imagine that the new "Sentinel" has made major advancements over the late-90's-era Predator.