People who choose to not carry cash because they think they can get everything they want with plastic are making a mistake. Twice I've been parked in an expensive downtown parking garage where there was no attendant and the connection to the credit card company was down. In another memorable case I paid a cash bond to be on my way for a moving violation. Let me hasten to add that this was not any kind of bribery -- the trooper issued me a receipt and when I won in court I got my money back.

Right now I have about $300 in my wallet, which is the minimum I like to have for significant travel. I recently returned from a business trip and didn't use much of my traveling cash. If we're going on a long road trip it might be $500.

For day to day I like to have around $200. This allows for a tank of gas, getting out of a downtown parking garage, tips for various purposes, a meal or two, and so on. It should be enough for me to get in an expensive city cab and get a ride all the way home, if I took the train or my car breaks down.