I garden on a hillside with very little topsoil, so everything is in raised beds, terraces and containers. As large pots increase exponentially in price according to size, most of my containers are unconventional to say the least.
I've used old-fashioned metal dryer drums, which have natural drainage holes for larger items like my blueberry bushes and pomegranate tree/shrub. Did I mention they're usually cast-iron steel? Those things last forever, and are great large planters that you never have to worry about rotting like half oak barrels.
Next was the BBQ pit planter made from a metal 55-gal drum. It was cut in half from top to bottom, and then welded to bent rebar legs. We discovered this gem hidden in the vinca on the hillside under our studio. You'd never have seen it from above, but I noticed it poking through the foliage while walking up from the river one afternoon. It was very rusted, which made it easy to snap off the welds on the legs, and let it rest on the ground, where it now houses orangemint and catmint to keep them under control and out of mischief!
The old, rusted wheelbarrow has had the handles and wheel removed, and snugged into the dirt. The goblin flowers, a type of blanket flower, don't mind the varying depth of the planter and have filled in beautifully.
My latest pots were unearthed in the vinca by my husband - two white ceramic toilet tanks! I had run out of places to put the zinnias acquired while I was in Fresno for Mother's Day and these provided the perfect solution. Nice depth, nice ceramic finish, drain holes - what more could a girl ask for?
Oh, I should mention my worm bin. Many people have those nice, layered, stacking affairs. Not my worms though. My worm bin is the body of an old refrigerator, sans door. We added drainage holes to keep the worms from drowning in winter. The beauty of the fridge is the sheer volume - with that much cubic footage, the worms have plenty of room to self-regulate according to the seasons.
If you are willing to be flexible with your potting options, you'll find there are many containers waiting to be found or repurposed.