I have a small rack I bought at the office supply store for holding binders or books. I keep it on the shelf over my table and my rulers are right there to grab.
My larger ones?? My 3x18 rulers just sit to the side of my sewing table (don't use these much other than lines for quilting). My large 6x24, 12x12, bigger ones, I just keep on a shelf next to my cutting table.. those aren't so organized.