Living where we do and having seen the effects of Katrina, we normally keep $300 in cash stashed during hurricnae season. If we think there is a serious chance we will have to evacuate or not have access to a bank for a while, we will increase the cash to $500 - $700. Other than that, it sits in the bank.

For personal emergencies, I always keep a $20 bill and several ones sandwiched between two dog tags on my key ring. Use a rubber silencer to keep 'em together. Other than band-aids and my Squirt, that has been the most used EDC item that I carry.