Currently, I am using heavy wire shelving. If you buy the good stuff, it will hold a lot of weight, and it has wheels: 800 lb with wheels 4,800 lb without wheels. These are a bit pricey. When I bought mine, I had considered making a wheeled lumber rack, but when I priced it out, I found that the wire shelf was cheaper. TRINITY 6-Tier Wire Shelving Rack, 48"x18"x72" is what I have. I only use the bottom half.
Smaller pieces go into a plastic box, and eventually, I cut them into small toys. Anything that is left gets burned in a backyard fire.
The only bits and pieces I keep are if darker woods I can cut contrasting trim pieces from.