I save the feet for stock unless they have bumblefoot.
Feathers compost nicely but it's much easier to pluck straight into the bag I'm putting the offal into, so that's where most of them go.
I do my killing right by my compost pile, so the blood goes there.
I clean the gizzards as mentioned above, and freeze them to either go into a batch of stock or to give to my father-in-law, as with the hearts.
Livers go to the dogs, except the duck livers; those I keep because surely someone likes those.
Intestines go in the trash.
Heads go in the trash too, unless one of my friends wants them. I have several that like to clean skulls for taxidermy projects or decoration, and I'll save them if they ask.