For those who prefer the debit card to credit card, simply because it is one less bill, or concern they will forget to pay - the First USA folks, which have the United Mileage Plus cards allow you to link the card to your checking, and have it paid every month on the final date due.

This won't hold down your spending, but it allows you to possibly earn interest rather than pay right away, and earn miles - without the possibility of screwing up.