I recall reading a series of blog posts written by someone who survived a south american economic collapse. (I forget what the URL was.) His perspective was that there is a VERY thin veneer on civilization, after which weapons, a fortified home, large cars, and absolute paranoia seem to be the best bet. Some highlights:

- small gold rings are good currency: you can easily divide it, and you can carry small amounts on your person. For some reason, people valued that more than paper money. - a black market for guns (and ammo) will spring up; cheap POS guns will have ludicrous prices, so if you plan to have one, it's wise to have them before The Collapse - Don't open your door for anyone. - Be armed. Seriously. - Be prepared to seriously consider whether to drive _through_ a pedestrian, rather than risk that his friends will kidnap you as soon as you stop. - Neighborhood friendships are extremely valuable.

.. that's all I can remember off the top of my head. I'm sure someone else can link the originals. Basically, though, it's comparatively easy to stockpile small pieces of gold jewelry ahead of time, and people will tend to accept it in trade. (Water/food/bullets/guns are of course even more valuable, but those aren't as transportable.)