http://www.junkcreation.com/from-aircraft-tire-to-horse-swing
http://www.ethicalsuperstore.com/products/fallen-fruit/recycled-airplane-tire-horse-swing/ is a source to buy the Horse, http://www.swingsets4outdoors.com/tire-swings.php?id=2 has a dozen different things you'll be impressed with, made from old tires!
Thanks to http://www.vintagesol.com/ for the link, as that is where I came across the airplane made from an old tire, and it's a very cool use of a tire that's at the end of it's first life, with very few things that can be done to get more use out of it.
Maybe you'd like to make a big art object from an old used tire? http://www.airecy.com.au/