Shelves are one of the more versatile storage solutions for you to add in a kitchen. Floating shelves placed down the length of a wall provide the same level of storage as a bookcase but don't add the same level of bulk, which is ideal if you if you have a small kitchen. A row of shelves under your existing cabinets can extend their storage capacity and give you a place to store items you want to have nearby while cooking.
By installing magnetic strips and panels on your walls, you can free up more space in your drawers and cabinets. Magnetic strips are good for storing a collection of knives or metal cooking utensils. Magnetic panels, actually just sheets of metal hung on the wall to which you can attach magnets, allow for storage of smaller ingredients, like small spice tins with a magnet super glued to them.
Pegboard, despite its rarity in residential kitchens, can be both a space-efficient and attractive means of storage. Good locations to place it are on the backs of cupboard doors, between the cabinets and the counters, and on bare portions of wall. To make the pegboard more appealing, spray paint it in a color that appeals to you and matches your kitchen. Don't limit yourself to just utensil storage on the pegboard; pots and pans work equally well.
Hang single hooks on the walls, such as to hang a potholder next to the oven, or hang them in a grouping, such as for mugs. Install bars into the wall where you can hang caddies of different sizes. You can also hang paper towels underneath cabinets, along with any high-tech electronics you use, to save space. Pot racks remove bulk from your cabinets and place cookware in the center of the room hanging from the ceiling, a space that is often underutilized.