One of the local cafés near me has that whole recycled furniture things going on, Apart from being a really great café with good food. I sat in one day and picked up a book from their bookshelf.
I just noticed, after a while, that they had lost the little knoblets that hold an the shelves up. So, for each shelf, they broke a pencil in 4, and used them as the knobs. It looked fun, and worked. It even looked like they gave more support than the original knobs were meant to.