I'm going to post this in all the heat-related threads just to be sure to get the message out.
I installed a mister in one of my runs yesterday. Today was the first time I have seen them NOT PANTING in well over a week. I was delighted, and I'm sure they were too.
It might take them a bit to get used to it. They were leery of it and all the bravest one were hanging back in the coop or out in the other, less shady run. So today I spread a bunch of scratch in the run and waited for them all to be out in it and too jazzed about the scratch to care about anything, and I turned the mister on. That did the trick--they got used to it and then hung out there the rest of the afternoon.
All these other tricks help too, but again, get a mister!