My shelves are just 6.5 inches high and 4.5 inches deep and they hold so much. I keep things I need easy access to in this often under-used space - salt and pepper shakers, sugar and creamer, assorted teas.
Although these were made and installed along with the cabinets, one could easily make open-backed boxes out of 1x6 pine or laminate board and screw them to the bottom of existing cabinets. I had them installed under nearly all my cabinets. I did have to select my coffee pot carefully to be sure it fit underneath. The shelves are also a great place for displaying collectibles. Below is a set of handcrafted pottery mugs designed to look like bent tin cans.
I also had a paper towel holder crafted in the same style and installed next to the sink. There is no doubt about it - this design is a very handy kitchen storage solution.
Check out Apartment Therapy: Beautiful and Creative Storage Solutions in the Kitchen