When we cleared out my husband's parents' home after they passed away, we emptied saltshaker after saltshaker, and each one contained a few grains of rice.
My garlic powder, onion powder, Penzey's Mural of Flavor and their Sunny Paris will cake, but I just open the jar and use a thin butter knife to break it all up. What I really hate is when the espresso powder cakes, as it is difficult to break up. I sometimes put it in the coffee grinder. None of this was a problem when we lived in Texas, with its dry climate, but I do like living in an area with some humidity, although admittedly not the humidity we have had this summer.
To keep cabbage that I buy at the farmers market fresher for longer, I wrap it tightly in saran and store in the refrigerator.