I am curious if BA offered hotel/meal vouchers for the flights they cancelled to
IAD? I seem to remember something about "acts of war" as being out of their control and no compensation is required by airlines. Does anyone know? If I was flying home and had to spring for an additional night,that could really add up.

Can't tell you if they did or didn't, but I can tell you that they were under no obligation to do so. Most likely they offered what's called a "distress rate" at some airport hotels. It's the same rate that the airline pays hotels for their own employees stays. Maybe some food vouchers. Again, if they did this at all it was a good PR, not because they had to.
Also, don't forget, just because the BA flight was cancelled, others still went ahead. If you were cleared by the security, there was always a chance of BA putting you on different flights/airlines.

On domestic flights in the US i think it is required (but im not entirely sure). On America West our flight was canceled, and they paid for our ticket, gave us a voucher for a free night at a hotel, a free ride to the hotel in a cab, and $250 cash per person. The only catch being that we were heading from Phoneix to Portland and we had to stop in Orange Co. and Oakland before arriving home.

Chaseman, the question was about cancellation due to outside airline controls. The airlines don't owe you jack if it's weather, act of war, and in this instance order of the government(if that's what really happened, we don't know for sure now). If the cancellation is due to a mechanical, the crew is missing, etc.. in another words, if it's directly the fault of the airline, you will get compensated.
As I already said, even though the airline doesn't have to do anything in the above mentioned situations, they will work with the stranded customers as much as they can.

AAFF doesn't need the backup, but is completely correct. Airlines are only required to provide meal and hotel vouchers is it was their fault that a flight is delayed or cancelled.

As an aside, note that even if it is their fault, they are not obligated to compensate you for loss of hotel nights or other activities you may miss because of any delay. That's the job of travel insurance.

Thanks to noflyzone and chaseman99. You guys are very informed in that kind of situations...For everybody at FODORS when is weather, acts of war,ATC which MEANS AIR TRAFFIC CONTROL, ANYTHING THE AIRLINE HAS NO CONTROL OVER IT...they do not have to compensate you for.It happens...Now when the plane is broken, pilots or flight attendants are missing or stuff like that..then you can inquire about compensation. That does not mean you are going to get it for an hour or two wait...be reasonable...if there is weather please dont scream. get the facts go to your seat and wait...airlines wont fly IF IS NOT SAFE