So I got this idea from another persons instructable and decided to do one of my own. His is here http://www.instructables.com/id/Pallet-shelves/ . I liked his but had never made an instructable and decided to give it a try. I needed to organize the camping and boy scout stuff that basically accumulates in my basement so these seemed like a great option. At $8 Each these are excellent.
FIrst off, you need to find wooden pallets and free is best! I got mine from a local roofing company. most of the big name stores wont give theirs away or use the new plastic ones that they have to send back on their trucks. Also you need a box of 3 or 4 inch screws and 4 six foot 2x4's per shelving unit.
The Pallets will have to be trimmed until the edges are flush with the middle 2x4's so the vertical 2x4's can attach evenly later.
You will need to also cut the pallets in half making two shelves from each pallet. I had to remove one board from each pallet to get my jigsaw to fit the area to cut. In this picture the center board was removed and the pallet was cut. my shelves all worked out to be 18in deep by about 42in wide. just make sure that you use pallets that match and your shelves will easily be the same size when you cut them.
this is how I layed out mine when I assembled them. I put the bottom shelf starting at 20in from the floor and the middle shelf starting at 43in from the floor. The top shelf I made flush with the top of the 6ft vertical 2x4's.
Each unit holds a decent amount of storage. They do rock left to right a very small amount so I anchored mine to the walls since I do not have a finished basement. This also keeps them from falling forward if climbed on by young'ns!