Let me preface this with disclaimers: We live in "high desert" of north-central Arizona (State Motto: "....but it's a DRY heat....") My wife started initially with pine shavings from the farm-implement supply company for the first year or so, but later experimented with something else:
DRIED COFFEE GROUNDS.
Somewhere (probably here?) my wife heard about the idea, and tried a batch in one of our two coops, in the trays/beds under the perches.
The concept is that it works like kitty litter, but since chickens don't urinate, it just lets the poop dry out, so you can sift it just like a cat's litter box--something we couldn't do with pine shavings. The grounds compost along with the poop, and I've never seen a chicken eat at the grounds (it's supposedly harmless, they just try it once and never again or something).
You can buy big 50-lb. bags of dried-out, compressed grounds at some feed stores, but if you're thrifty and strike up a relationship with a coffeehouse, you can conveniently take their coffee grounds daily, often bagged in a giant filter bag over the course of a day. A drive-through coffee stand is a third of a mile from our place, and I make a nearly-daily pick-up, place the bag on a rack to dry in the sun, and now that winter is upon us I'm experimenting with using my large propane-fired smoker as a drier. I manage 2-3 five-gallon buckets a week, on average. When we do a full clean-out and replacement, the grounds and poop go to a huge compost pile along with some grass, shredded weeds, the chicken poop, an occasional dusting of lime to neutralize the acid, etc. (I've also started light dustings of powdered/granular agricultural lime with a grass seeder through the runs and coops every few weeks to help keep odors down.) It's only become compost after weekly waterings and turnings; before it had been ignored by the in-laws and turned into fossilized poop/grass. Now with the coffee added, it's a rich festering compost pile.
For their kindness in letting me "steal their trash," the coffee stand gets rewarded with a LOT of daily purchases from my wife's co-workers nearby, and fresh eggs once in a while for the workers there. (In spring I'm competing with people mixing potting soil, so....)
We still use shavings as part of the nesting material in the nestboxes, bottomed out by "fake grass" mats and carpet samples.
As for the runs, we have the extreme luxury of having the ten-acre plot covered by 25 large truckloads of mixed mulch, dumped with our permission by the county (for whom the one brother-in-law works) when the county ended up with so much mulch it had to truck and dump it at any ranch willing to take it. So we have plenty of mixed-wood mulch, aged 1-2 years, to make life a little softer than the rock-hard dirt parched by drought that otherwise would be at the bottom of the runs. We have to toss larger chunks to the woodpile, but I've never seen any ill effects to the chickens' feet. But we leave enough dirt exposed for the chickens to dig their baths as well. And the free-rangers who make it to the outlying mulch love digging for bugs and worms and the like.
UPDATE with care notes: If you do not dry the coffee THOROUGHLY and/or if moisture gets into the grounds, the grounds can develop mold (green, in our case) and need to be changed out. The biggest culprit in our grounds is the occasional clump of damp, pressed espresso powder, which if not broken up and spread stays wet and will act like a "mold seed" to start mold growing. The mold manifests itself as large clumps of grounds stuck together like damp cat litter.
(random but i thought i should say it sense some people are using it where we live. Im not sure if its for everybody, but thats what ive heard and we dislike using it)
