I made these storage units yesterday.  I was tired of looking at the fabric and yarn stuffed into the shelves, so I put them in boxes!
Here's how I made 'em:

I went to Office Depot and bought the 9x9x9 corrugated cardboard boxes because my boyfriend and I made the shelves to fit perfectly under the lip of our window (our kitty sits on top of them).  So, box size will vary depending on your space.  I know I probably could have hunted around and asked at stores for spare boxes, but I had the organizing itch and it was a beautiful day to ride my bike to the store.

I cut off two of the flaps on top...  I'm hoping to put a button on either flat and wind some yarn around them to keep them shut.  Right now, they work fine in the shelf.

I measured out the wrapping paper that I bought at Target and glued it on.  I didn't put any on the "lid" or the bottom.

And finally I went through my fabrics and cut a little square out of the corners and taped them onto the front of the box.  That way I can feel the fabric as opposed to just having a picture of it (which would have been more time-consuming).  The same goes for the yarn. 

I'll go ahead and make a separate post for the stackable boxes/shelves I've made.