Make fridge mats out of regular placemats. So brilliant! This makes cleaning much easier. We currently have those wire-looking shelves instead of glass shelves, and something like this would be awesome.
My number one secret for fridge organization is washi tape! It's a great way to label foods, including the date cooked or best before date. I use different colored washi tape to label leftovers, ingredients, etc... to avoid cooking mix-ups.