Some 350 tons of high explosives (RDX and HMX), which were under IAEA seal while Saddam was in power, were looted during the early days of the US occupation. Like so much else, it was just left unguarded.Better yet, the Department of Defense has been trying to suppress this story for some time.
Not only are these super-high-yield explosives probably being used in many, if not most, of the various suicide and car bombings in Iraq, but these particular explosives are ones used in the triggering process for nuclear weapons.
This joins the cheery news that nuclear materials from Iraq disappeared as we also left those facilities unguarded to go off and be pelted with flower petals. (Of course, we haven't secured our nuclear and chemical facilities at home against terrorism either, so maybe Bush "just isn't that concerned" about such things...)
Update: And we also shouldn't forget that the Pentagon had Zarqawi's location in their sights more than once, but the Administration politicos put strikes on hold until they could build momentum for action in Iraq. Good show of priorities there...