Particle board and plywood are composed of pieces of wood products that have been pressed and glued together. Although they are popular siding materials for storage units, they are not most people's first choice in regions where it rains a lot. For if water does work its way into these products (a possibility enhanced by their composite nature), then you're lost.
Utilized Pegboards - Pegboards are a great tool that can be used almost anywhere in the home for organization. The same is true for your shed. For small tools, such as hand shovels and rakes, attach a pegboard to a wall and use various hooks and hangers to place hand tools and other items on. This gets them off the ground, out of the way and in a consistent spot that is easy to find.