The Northwest Airlines card will give you 15,000 miles up front for free. That offer was still available as of a few days ago.
There are lots of cards that will give you 1,000 -10,000 miles up front for free. The Delta American Express card gives double miles for some purchases. The Starwoods card gives 1 1/4 miles per dollar spent if you convert its points to miles in 20,000 mile increments. Delta is giving an extra 5,000 miles for such a conversion through October 31.
Info on all of this is on the Credit Card page of my web site below.
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Free Frequent Flyer Miles