if you have any of these in your linen closet ........
Over the years I have saved the clear flexible vinyl 'bags' that new pillow cases, sheets, curtains, bedspreads are sold in. You know the ones that snap close or zip close? They make the best packing cubes. They are sturdier than ziplock bags and have lasted a long time, and therefore I saved somethings that otherwise would have gone in a landfill. Since I have them in various sizes, they have become a staple for my trips.
By the way I keep the emptys inside the suitcases when one trip is over so I don't have to look for them when packing for next trip.