The Delta Airlines Skymiles American Express card will offer 20 to 25 thousand bonus Skymiles (Frequent Flier Points) when you first sign up. However, once you have signed up for a card, collected the miles, and then canceled the card, they no longer give you bonus miles for signing up again.

However, Northwest (NWA) and Delta are now in the process of merging. If you have a worldperks account, you can transfer it’s miles (points) at a 1 to 1 ratio into your delta account (after linking the two accounts). NWA also offers a WorldPerks Visa that gives you a 20,000 mile bonus for signing up. So, if you apply for the WorldPerks Visa, and purchase something with it, you get 20,000 miles in your NWA account, which you can then transfer into your Delta Skymiles account. (If you decline to give them an email address, you get a flier with a URL in your first bill that offers another 500 bonus miles if you register an email address.)