What's the best credit card that offers free airline miles?

My wife and I travel a pretty good amount and were wondering what credit card offers good frequent flyer miles. What do you use?

We travel in the US a lot.

I don’t know if it’s the best way to go, but I use a MBNA Amtrak CC, which you can use (convert) as airline miles in groups if 5000. IIRC it’s 1mile/$, or 5miles/$1 spent on Amtrak.

We’ve had good luck with Providian’s Platium Visa. Not frequent flyer miles as such, but “rewards points” that can be converted to hard goods or airline tickets. Just last week we cashed out all our points (about five year’s worth) for a pair of roundtrip tickets from the West Coast of the US to London this fall. Since we used the card only to buy the stuff we were going to buy anyway, and pay the balance off each month, our only expense was the annual fee for the points program - something like $48, IIRC.

Oh, and my wife cashed in some points two years ago for a roundtrip to San Antonio to see her daughter graduate from basic training in the Air Force, which went smoothly. We had to use Providian’s choice of travel agency to book through, but that was no big deal.

Just to add, no anual fee with this one