The folks at My Roman Apartment blog vowed to "Buy Nothing New For One Calendar Year," but were stuck when they realized that they didn't have any containers in which to plant new seedlings for their garden. The solution? Hulled out citrus rinds. Since they live in California, citrus is quite plentiful thorughout most of the year.
Here in Florida, this would also be an easy, low- or no-cost project (if you don't have a citrus tree, it's very likely that a neighbor does as they're everywhere).
The instructions are simple: Take a hollowed out citrus fruit half, make a hole in the bottom of the rind for drainage, fill it with soil, add a few seeds and give it a little water. And when your sprouts are getting too big for their citrus planter, then simply transplant them to the garden.