Hold on Tight bookshelf. A brightly-coloured aluminum cube and oversized wing nut serve as a sliding bookend which can be adjusted and secured wherever it is needed, whether your book collection is growing or shrinking.
Cheap wooden boxes as containers, stacked on top of one another. They're held together by binder clips. You can buy paint from a craft store to paint them if it's in your budget; if not, colored construction paper would work great too.