I meant to note this Washington Post story from the weekend on the second Samarra bombing not causing the sort of wide-spread blood-letting of the first. The surge apparently has had something to do with it:

Analysts said that many lessons have been learned, and circumstances have changed, since the February 2006 attack.
In particular, thousands of extra troops were on the streets of the capital this week because of a new U.S. security plan, and the government immediately imposed a four-day curfew, as opposed to 2006, when the government did not act until after the sectarian backlash had begun. In addition, the extra Iraqi troops currently in Baghdad are mostly from the army, which is less sectarian than the Iraqi police force

But al Qaeda is still at it. Here’s the latest barbaric attack on a Shiite mosque.