I have some old pillows that I needed to recycle and didn't know a thing about it. I knew enough that nobody really wants to sleep on a used pillow and couldn't think of anything else to do with them. I hit the web and here's what I found:
Many veterinary clinics, pet hospitals, and pet boarding facilities accept old blankets and pillows. They use them to give the animals something other than a metal floor to sleep on.
You can also take off the pillow cover and either buy a new one or make a new one to match your needs. This would save you from throwing your whole pillow away and also save you money on a new looking pillow.
Some homeless shelters will gladly accept old blankets and pillows. This is where I ended up taking mine. I didn't just help the environment, I helped a person in need.