Step 1: Materials
1) Cheap plastic containers with holes in the sides. (I work in the produce section of a grocery store, and we had some produce come in the containers, so I took these home since we only throw them away. You can check your local grocery store or even local convenient stores to see if they have any that they may be throwing away or don't need, or even find some to buy in any store)
2) Plastic zip ties, aka cable ties (I also found these in our tool bin in our department, so I used a few of them. If you can't find any from a relative or friend, you can get them extremely cheap at wal-mart or basically any other store, even sometimes gas stations for a little more)
Step 2: Stack 'em Up!
Step 3: Tie 'em Down!
Step 4: Repeat "Stack 'em Up!" and "Tie 'em Down!" Until Satisfied!
**Some last minute notes and suggestions that I came across when building my own....***
There were a few things that I came across with my own design, and these suggestions may not even apply to your own design, or they could possibly help you out. First, I had some problems with the zip ties that I found, they weren't the best quality and they kept breaking on me. I recommend, if you are buying your own, to get some higher quality ones, not the off brand ones. They also make some that you can reuse again, if you plan to use the containers other than a book case, when needed. Another thing was that my containers weren't as sturdy in the front as they were in the back. This may not be a problem with your own, but if you can, find some that seem really sturdy altogether. You also could add something solid to the sides or all around the book case, like attaching some boards or some sort of plastic sheets or cardboard, to add more support to the sides and keep it from swaying (which mine do a little) and even make it look nicer. And one more problem I had, was that my taller books would not fit in my containers standing up, so here are some options you can try. You can either lay these books on their sides, which can work as a book end if you don't have enough books to fill up your container, you could cut the top section off the top container on your stack, to allow the books to have more room and not be limited to how short your books (if you plan to have a really tall bookcase, you may want to think this over if these taller books are really heavy, this could cause some injury if not careful), or just get taller containers. I hope that would help you out with some possible problems that you may have. Thanks again for checking out my instructable!