I really like the Invisi-Grip to cover the bottoms of rulers. It is a vinyl cling product that one cuts 1/8 inch smaller than the ruler. It doesn't throw off the balance of the ruler.
Also, the rubber ring BobbinSaver is terrific for storing bobbins so they don't unwind. They slip so easily in and out, and you can see the color of the thread at a glance. Both of these items are available at JoAnn's.