you have to drop the items to the ground, go out of the house and into the house again. most stuff should stay in place after that. there are still a few pieces that do not (nettlebane, the emerald dragon claw...).
Just to elaborate on this. Drop the item on the ground, leave the house, come back, then move it to where you want without putting it back in your inventory (so you have to drop it again). It should stay in place.