Add a round turntable, so you can twirl things around to the front where you can reach it.

Use the shelves that are made for holding dishes and baskets back there. I have all my extra boxes of baggies and my extra foil wrap and that sort of stuff under my shelf It is 9"x 14" I have baskets on top that holds extra spices and lots of other things, and the baskets give me easy access because I can just lift it out.
I have another one that is the same size and my 9X13 baking pan with others stacked inside sits on the bottom and my round cake pans and pie tins sit on top. These little shelves organize a lot of stuff and it all makes for easy access.

On the bottom shelf I store occasionally used pots and appliances like my crock pot. I have a lot of tall dollar store containers that hold baking stuff--left in their own bags and put in the container. Things like icing sugar, coconut and chocolate chips. Cereals too have their own container. The containers keep them fresher than their boxes. Other containers hold other stuff. All the containers are labelled with the label facing the way they are stored in the cupboard. I can see at a glance exactly what I want.

In fact I think the key to any organization of cupboards is containers of some sort and labels.

Ikea has a nice version of the turntable, it is a carousel that spins out of the cabinet

Here is a link that might be useful: Ikea carousel

Why I prefer shelves to a turntable----

My son has a turntable --I have shelves.
You can put less on a turntable than you can on shelves. You are still moving things around to get what's in the middle of the turntable. Things fall off of the turntable and you end up on your hands and knees trying to fish them out. It's harder to clean the cupboard itself.

My opinion only, but I thought I'd throw it in here

Thank you for all your suggestions! I agree with oilpainter that turntables, unless the built in kind make a small space even smaller and more difficult to navigate. Right now I have some wire shelves and a wire drawer storage unit in one. It is just so tight that I hate having to look for anything and my first instinct when putting things back is to put right inside the door.I may convert items to baskets so I access it with less of a struggle.

One idea: put a basket way in the back, to hold stuff that needs coralling, but that you wouldn't use all that often. And yet, when you need it, you're willing to go to some trouble to get it out. Spare sponges, spare plastic wrap, pastry-bag & pastry-tip set, stuff like that.

Then, in the space where the basket would have to move *through* in order to get it out, set something big and single, like a stockpot. Something that you can just pick up one-handed and lift out of the way when you need to pull the basket "drawer" out to get the stuff in it.

Or, put the stuff you use only once or twice a year there--turkey roaster, etc. Out of the way, seldom disturbed, but important enough that when you *do* need it, you will go to the trouble of getting it out.

I think on the kitchen forum, they had some pics of someone who put in roll out shelves way back there. Two shelves that pulled sideways or something. I think this is a great idea!