They are available at farmer's markets for just a few cents in all sizes and colors. I have a couple of baskets in my office that resemble the tall bongo drums used in Ricky Ricardo's band. Bushel baskets are among the best, disposable containers for growing all kinds of plants. They come with handles, naturally drain well and look good on the porch, patio or deck. Try growing two or three cabbages in a basket and maybe even place a small annual like alyssum in the pockets between the plants.
Peppers also work well in a basket and can be interplanted with leaf lettuce.
For extra fun, try growing cherry tomatoes in a basket, and let the vines cascade out over the edge like you would a lantana or purple wave petunia. My son James still talks about the time we planted Irish potatoes in a large basket. This might be just the way to get your children started in their first gardening project. For a really awesome basket that will be the envy of fellow gardeners, try lettuce in a wire hanging basket. Get a wire basket and line it with moist sphagnum moss.