I ran into a nice video on building raised beds with recycled pallet wood. Your mileage may vary in that you might not be able to find pallets with the same dimensions.... but you are smart and can probably adapt this video to other scrap wood that you might be able to acquire.
Enjoy. Our raised beds are made from cinderblock and are probably more durable than wood, and we are pleased with them, but they cost more, and they were quite a bit of work to build, especially the capstones.
Also, re-claiming pallet wood: