I'm wondering which services or departments had offices in the section of the Pentagon that the plane hit.  Does anyone here know?

There really is no standard.  I worked there from about 85 to 88 during summer work and the JCS (Joint Chiefs of Staff) are over near the river entrance (East side) corridors 8,9. Same with the NMCC.  But I'm not sure if they moved that below ground since my time there.   Air force was mainly on the 4th and 5th floors.  No specific corridors.

The secton which was hit was being renovated, or was just finished so casualities should hopefully be lighter than what it could have been.

Btw, it is still burining and on the way into work today, I smelled it from 3 miles away.  The smoke is drifting over 395 and cars going into DC get a nice whiff of the smoke.

Thanks for the info, 7.

BTW, I wonder if potential targets such as the Pentagon are going to be protected by barrage balloons (such as those used during the Battle of Britain).  They aren't as sophisticated as surface to air missiles, but they are much cheaper and they have the advantage of only being able to damage aircraft that are already too close for comfort.

I spoke last night with a friend that works in the area. He related to me that he had a meeting scheduled yesterday IN THAT SECTION. The meeting was moved to another location and the 4 Army gentlemen that were in the meeting said that the meeting saved their lives. He also said that many of the offices were Army in that area.