Ash is turning me into an Elfa® fanboy. These shelves are sold at The Container Store, which we used to shop at a lot when we were living in GA. They are custom-cut for your measurements and completely modular/customizable, meaning you can hang up some shelves, then move them up or down as you need to.
The first project in our new home that we did using Elfa® shelves was the laundry room, which just had one long shelf over the washer/dryer. We converted this to three shelves, which added a ton of storage space in our tiny laundry room. This was my first Elfa® install, and I understood then what Ash saw in these shelves. They were wicked easy to put up.
So then we decided to do our master closet, which is not really a walk-in, but yeah you can walk around in there a little. Basically what we did was split the long wall into two shirt-length hangers and a single hanger for pants, with shelves on top. Before it was just your typical one shelf with a hanger below it across the whole wall, which is just so much wasted space.
To be fair, I should mention I think you can buy this kind of customizable and easy-to-hang shelving at Lowe's/Home Depot, but when we went there to get something for our laundry space, they weren't able to cut the shelves to fit our dimensions.