My mom always used jeans to make potholders. Several layers of denim cut into circles, sew around in a spiral to secure the layers, and bind with bias tape. They last forever and really block the heat. I have used denim in the middle of potholders made with regular quilting cotton tops.
I also have made "saddle bags" for the four wheeler my husband uses around the farm, to hold his pliers, etc. You can buy them, but for much more than an old pair of work jeans costs.