Like shipping pallets, wooden cable spools are another item that is usually found for free on Craigslist. Since cable spools are limited by their shape there are fewer repurposing options, but they make a great coffee table bookcase.
Crate Storage: Wooden crate converted into a portable side table with storage - love this creative idea. Easy to make: Turn crate sideways, add a couple of internal dividers & screw 4 castors on the base. wheels for me)
DIY vintage trunk to rolling bar project. The idea of cutting up vintage luggage for crafts irks me almost as much as the idea of cutting up vintage books for crafts. However, this is amazing and I'm not doing anything with those trunks anyway.