Kids' shelves

OK, we all know how hard it is to keep kids' shelves organized and looking neat. These two pictures are from a project I worked on recently and they show my general organizing principle of keeping like with like. This makes clean up much easier--it's hard work, but I have been working with my kids about putting stuff back where it goes. The two boxes on the shelves in this picture jazzed things up a bit and I got them at Marshall's. I also think it's fun to rearrange shelves now and then depending on the changing interests of the kids. My four-year-old likes to collect things like rocks, shells, sharks' teeth, etc. I am constantly looking for the right containers to store these collections and haven't found them yet. I would like the container to be clear and plastic so they can easily see what's in them. Let me know if you have any ideas...