I purchased a few plastic shelving packages from Home Depot and began to clean and toss out what was not being used. You can see below what the space used to look like. Don't ask what was going to be done with that huge gourd in the corner.
Below you can see what the space looked like after I tackled it. Since I got rid of so much junk and old boxes, I did not have to utilize the space in the very back of the cabinet. In addition, it only took me about one hour to clean out the space and reorganize it. My cabinet under the stairs project is a good example of what can be accomplished in an afternoon with only about $60 worth of shelving and some knee pads.