[MaryLou]

This is such a great idea, and no-one told me about it when I first started keeping hens, so I am passing it on. 
I saw a run with a straw bale in it last week.  I have a decent-sized run for my four new hybrids (Sussex, Maran, Blue, Leghorn) and although they have a lot of time in the garden, they also spend quite a bit shut in the run.  I put three bales in last week (artistically arranged, one on top of the other two, they look quite good) and the hens love them - pecking/exploring/sleeping/and standing to survey the world.  I can hang their treats at different levels which helps reduce competition. You can also carve a hole in the middle to make an extra place for birds to perch if you want. 
I intend to continue to pick droppings off each day, but I do that in their house anyway so it's not really difficult with only four birds.
Not sure how long the bales will last - be interested to hear from others who have tried this or have other ideas for keeping hens busy in their homes.

[Sassy]

They love lining up along logs placed in their coop as well as hopping on and off.