First you need to decide what type of storage you want. Are you looking for some place to store books? If so, you might like to build a bookcase the whole length of a wall. That way you can use all the space from the ceiling to the floor.

If you are looking for more wardrobe space and don't have room for more furniture, why not build drawers along one wall in the bedroom? This will give you room to store not only clothes, but also any other items that are small enough to fit into the drawer. If your bedroom space is limited, mount your TV on the wall using special wall brackets, leaving your floor space for other items.

Large families always run out of towel space, so make a ladder of rails using dowel rungs glued into place. Propping the ladder against the wall will let the towels hang away from each other. You sometimes see a Lazy Susan on the kitchen cabinet holding a variety of goodies; well the same thing can be done in the bathroom. Just think of all the small items you have lying around, taking up space that could be used for other purposes and also be more organized.

Building seats under the windows or all around the wall will give you extra storage, and also a place to sit. This would save having extra chairs sitting around. Get creative and see how you can better store small items to create more useful household space.