I do some light gardening, but haven't done any as of late. I started rebuilding my garden following an above-ground model and using cinder blocks/decorative blocks to build it. Ran out of time, season and money last year. Don't know if I can get it put together in time this year.
Previously, I constructed huge planters (4x4 or 4x8) boxes using clean discarded pallets. Using three pallets would yield one planter. Unfortunately, the planters don't last more than four or five years at most, but not an issue when you have plenty of pallets to use.