False Top (or Bottom)
When you build a piece of furniture, build in a stash spot. For example, when you assemble a dresser, put a piece of 1/4-in. plywood just above the top drawers and install a piano hinge on the top. Now you have a spot to hide precious items.
Spread Your Wealth
Use lots of hiding places. You could keep cash between pages in books, tape an envelope behind your headboard or put cash behind the false panel in your dishwasher.