My buddy beat drug dogs at the canadian boarder by putting all his drugs inside baggies inside peanut butter cans (or tubs or whatever the hell they are called). I wouldn't say this is fool proof, but it worked for him once. They got him for paraphanalia cos they found resin in some pieces he had, but they never found enough to get him for possession.

Side note... if it works good enough for drugs dogs, think how well it works with parents/school officials etc. Plus peanut butter doesn't look nearly as suspicious as a can of coffee grounds. At college we leave the peanut butter jar out in the open, and the RA's are none the wiser.