My girls love turnip greens. I have a vegetable garden that, at this point, is about 80% turnips, and the greens on the big turnips are easily a foot and a half long. I usually harvest one turnip a day to cut up into sticks or mash with supper or what have you, and tear the greens off for the hens. 8 hens make quick work of a turnips worth of greens. I also give them chard from time to time, as I'm growing it for the first time and discovered I don't like it. But they do.
They get a lot of kitchen waste. Any stale bread or soft fruit and vegetables go to them.
Their favorite thing seems to be earwigs, though. In this part of eastern Canada, earwigs (http://en.wikipedia.org/wiki/Earwig) live in every dark crack and crevice, and the coop certainly has its share of those. Whenever I open the run door, or the egg door, or any other flap on the coop, a dozen earwigs fall from the cracks and the hens peck them up voraciously. I'm hoping that their efforts will, eventually, eliminate the earwig population in and around the coop.