It depends on what the item is. Food items can go in the larders; some of the plants can go into the crafting tables or the surgery table; minerals can also go into the crafting tables for the witch or to the blacksmith's forge. There are probably others that I have forgotten. You can also sell off a lot of your items or donate them to the blacksmith or the merchant to sell. I am a commited collector- I can rarely resist a rock pile or herbs to gather or fish jumping in the pond but I never feel as though my sims' inventories get too full. What is it that you want to store?