Domestically, just what i always carrry. Amex gold for food, CSR for travel expenses, and whatever card I'm currently working on a bonus for (for other expenses). I may also have the Amex Hilton card if I'm staying at a Hilton. And an ATM card.
Overseas, I usually just take the ATM card, the CSR, and another backup card (usually the Amex so that I can use travel services in a pinch).