My mom hand stitched a double knit quilt years ago. It is the WARMEST quilt in the history of the world. Think frozen tundra warm.
My grandma used to make cool rugs and pillows from squares of double knit. You cut about a zillion 1.5 - 2 inch squares. Fold them into a triangle and layer them in rows or spirals on a piece of heavy cloth. Depending on the color choices they can be very pretty.