Perhaps no one described this dynamic better than the late, great Dr. Julian Simon (c.f. The Ultimate Resource).

First the “coming economic chastisement” site you link to above has some good ideas, but they are really too little, and some are just not related at all to making it through bad times. In the event of an economic depression, these are your practical priorities: food, shelter, water. If the air has gone bad, there’s really nothing affordable one person can do about it.

An amazing amount of food can be foraged in any civilized locale. Fencerows, railroad easments, stream banks, vacant lots, all are frequently populated with edible plants, from apples and blackberries to mustard and poke salad. Give it a try some time (not in March, but in June and August). A great many suburban yards have plum and apple trees with bushels and bushels of fruit going to waste every summer. I can often be had for the asking, especially if you show up with 2 or 3 clean, well-dressed kids in tow. Before we moved to the country, we would put up 40-50 quarts of applesauce and 20-30 pints of blackberry and huckleberry jam every summer, all of it foraged.
Learn to identify wild foods, particularly greens like purslane, miner’s lettuce, and mustard. Stay away from mushrooms unless you really know what you’re doing. camping trips are the perfect opportunity to practice.

Food preservation is mandatory. Learn to can, and to dry foods. Start now. Drying is easier, and can readily save you money. My brother buys cheap produce on sale and dries it over the heat vent in his kitchen. An hour spent chopping onions and two days of drying tuned 20 pounds of perishable sweet onions into 2 pounds of dried onion flakes. The dried onions will keep indefinitely, as long as they’re dry.

Shelter is tough if you haven’t got any. Convenient places in urban areas, such as road overpassses and remote areas of parks are typically already occupied by predators, the insane, and drug abusers. If you have kids, that’s the last place you want to be. It’s far better to staying with family and friends, or failing that, out in the country, or even the remote forest.
Part of shelter is warmth, and that means fire. Learn to maintain a campfire, and to cook over one. A proper dutch oven will be a huge help in that regard.

Most people don’t think about their water supply, but you’ll really miss it if it’s gone. The good thing is that purified water is these days available from a dispensers at grocery stores and walmart for as little as 30cents/gal. The bad part is when .30 is more than you can afford. Surface water is usually unsafe to drink in any area of the country, but with the addition of 1 teaspoon bleach per gallon, can be made safe for washing yourself and your dishes.

The ideal solution is to have land, a deep well and no debts. Even a small yard can provide a huge amount of food if it’s managed right.

One thing the blogger at “the coming economic chastisement” does have right is the necessity of sharing what you have. Remember the widow’s mite. It’s a laudable thing to give of your surplus, but to give of your need earns you merit in the eyes of our Lord himself. Sharing not only works to your spiritual benefit, but to your practical benefit as well.