I built the lumber rack detailed in this link to a Shop Notes Special for 10 projects form 10 sheets of plywood
I used one sheet of birch plywood (really too pretty for this project, but it was on sale and I'm so sick of the crappy borg stuff). Due to some sillyness on my part, I had to cut away the bottom shelf and re-cut the notch for the cleat to make it fit the space in my shop. I've got it loaded down and it's working great so far. Super cheap and easy, especially if your shop walls have exposed 2x4s.