The seat of choice for me is a tri-fold with a back support . It gets you up off of the ground and very comfy. Nestle in between some blowdowns and enjoy a morning hunt in comfort. These old bones are thankful !
For years I have been using a Mossy Oak Inflatable Seat/Cushion. They are very lite-weight, have an adjustable strap to wear around your waste or quickly buckle to a pack. http://www.bowhunterssuperstore.com/allen-self-inflatable-breakup-camo-seat-p-4841.html
They do not make noise and the cushion is adjustable by adding or letting out the air inside. If you get the wet they dry out quickly. There is no back support but that's why god put trees in the forest.
Thanks for all the replies. The one that I had was a square cushion that I purchased from a Sportsman Show years ago. It was nice and light with at least a 2 inch cushion and no matter where I hunted, it was with me. I used in tree stands and on the ground.