I've talked about my binder system before, but it's been at least a year. I thought I would share how I store 3-part cards and printables, and then share some other methods that I found on the internet.
These six binders (I think they're 1.5" wide) hold all our theme units for the year. The color is just for fun, and the spines list which unit is in each binder. You can see all our units from this year here.
Each theme has a unit cover in a page protector. Behind the cover is a clear zipper pouch. Unfortunately, these pouches are discontinued, but these are similar. I put a few lines of machine stitching on them to distribute the printables better and help the binders lay flatter. All the cut printables are in these pouches, then I have page protectors with all the other papers in it. There might be a better system, but this has worked very well for us. I love how little room it takes up and how it can be hidden in a kitchen cupboard.
Here are some ideas from around the web:
This fabric one is lovely and functional. I like how many options you have in using fabric- so many fun patterns for all the different subjects.
I have a lot of felt products on this blog, so you know I love felt things. This folder is so beautiful, but I can't imagine making twenty or thirty of these to accommodate a whole collection.
These little folders are similar to the set up that I had when I first started Montessori. I liked how they all fit in a CD box.
I find this set up very inspiring. I love how it has a place for the control chart on the left and the pictures, labels, controls, and definitions on the right. The big folder is the back-to-school special, fifteen cents, plain paper folders. The little envelopes are library pockets, which you can get in many designs and colors. A whole pile of these could be put in a file cabinet or an accordion folder.
This is an even simpler system, especially if you had room for the container to sit on your shelves at all times. I like the way it looks, though.