CNN has this article on "recession gardening" -- although I think I prefer the term "Victory gardening."
There are a number of benefits to growing your own food. It's great exercise; it tastes better and is more nutritious; it saves you money on your food bill for a minimal financial investment; it's educational to your children; there's less concern of contamination with pesticides or bacteria; it's an important life skill that helps you reduce your dependence on others; it's better for the environment because you are not buying food that has been trucked halfway across the continent.
If you are thinking of planting a garden, consider raising your plants from seed rather than from transplants. The transplants you buy at your local nursery are likely hybrids, that is, a cross between two different species of a plant. If you try to save the seeds from a hybrid, it will either be infertile or will not produce "true" to its parent. Heirloom seeds, on the other hand, are not hybrids, and will produce true to their parent. Also, in the event of a real crisis, you may not be able to simply go to a nursery and buy transplants.
Here are some resources for purchasing heirloom seeds:
Seed Savers Exchange
And if you want to make an emergency seed bank part of your survival items, here are some great options for long-term storage of a variety of seeds to feed you and your family in the event of a Long Emergency:
Survival Seed Bank - this seed bank has great, sturdy long-term storage that you could even bury if you needed to hide it from confiscation or theft.
Survival Heirloom Seeds - has different kits depending upon your living situation -- urban, suburban, family, homestead, or farm.
Finally, saving seeds requires some know-how. Seed to Seed by Suzanne Ashworth is the recognized leading authority for learning how to save vegetable seeds.