All I know is that the last time this happened people were snapping up Krugerrands because they are exactly one once of gold.
You can also buy ingots, which are smaller and more easily handled. If worse comes to worse, you can always trade gold for food - try that with worthless paper money. I would stay away from mining stock or certificates. If the bank on which the certificate is written goes under you are out of luck, and mines can go bust pretty quickly.
You can also buy these
http://www.usmint.gov/mint_programs/american_eagles/index.cfm?action=american_eagle_bullion
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"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"
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