I throw my boys' hair cuttings outside, and use my own hair from the hairbrush. Because it is so long, I cut it into several chunks before putting it into a suet cage. We got the Orioles to stay for nesting when they used to leave when the urge hit. They like horse hair and we have neighbours with horses on the other end of our section. And Chipping Sparrows used to be called Hair Sparrows for a reason.
We don't often use yarn, but one of the children's play things was attractive to a robin. He had a stick with a long piece of white yarn attached to it that was just laying in the yard. He saw the bird's struggle, so cut the yarn up into little pieces.
We had to help this Oriole and put a suet cage full of hair near this spot.
We save our duck's molted feathers for the birds. Most often Swallows take to them, but we had a Robin fill her nest with them one summer. The birds do not use the large wing feathers, but most of the others are about the right size.
This was not one of our feathers, but a Great Horned Owl feather one of the children found in the yard. I flang it into the air after taking a picture of it. And here comes Mrs. Tree Swallow swooping after it. She had a struggle to get it in, lost hold a time or two, when Barn Swallows came after the feather, but finally she was able to get it into the box!
what a good reminder for us to help our bird friends in this way. I use coir (inexpensive in my area which is filled to bursting with coconuts) as mulch, especially in container plants and the birds love to snitch this, including the hummers) and carry some off for nesting. They are not always particularly tidy about it but i don't care. Big birds, little birds, who knows what else, but it makes me really happy to know that the garden is supporting the birds in this way. 
