In BOB, not in PSK:
Gel-packs from runner's stores -- pure electrlytes & the right kind of quick energy used by marathon runners.
Seasonings: red pepper, black pepper, garlic powder, soy sauce in plastic take-out tubes, tabasco, seasoned salot -- anything to make whatever you scroung taste good.
Peanut butter in tubes; locally produced honey put up in tubes you get from the container store.
Good quality loose tea -- compresses to nothing, and is good for what ails you. Everything looks better after you build a little fire, make a cup, and think about what you're gonna do next.
Pack food in liter size nalgene bottles. Keeps food in, everything else out, and you can never have too many good water containers. If you are really OC, you can pack loose rice around everything else -- it won't shift around that way.