Great news!! Free Shipping is now offered on Mel's Mix - Square Foot Gardening Soil Mix at Home Depot online - huge progress!!! (you have to order at least $45 to get free shipping).
P.S. I get no reimbursement for promoting this - just spreading the news!!
This is the official Square Foot Gardening foundation soil Mix.
Square Foot Gardening Potting Soil Mix is perfect for any of your garden soil needs. Highly recommended for flower and vegetable gardens.