This is an easy one, but has nothing to do with GP. pgary offers information about this topic at length. Here is the relevant excerpt that answers your query:

American Airlines offers a free MasterCard that gives 2500 miles up front, and then 1 mile for every $2 spent. I was given this offer when I threatened to close my account to avoid an annual fee. It is called "Citi Bronze Advantage World MasterCard". I can't find it on line. You may have to be a bit persistent to find it, but it does exist. First try the standard number for applying for Citibank American Airlines cards, (800) 359-4444. If that doesn't work, call customer service at (888) 766-2484 and do not respond to any of the prompts. Instead, wait (several minutes) until the system gives up trying to understand you and sends you to a human being. In both cases, you will most likely have to ask for the card by name. Most reps say they have never heard of it, but they all have the means of looking it up.

The Amtrak Guest Rewards program offers a free MasterCard credit card that provides 500 bonus Amtrak Guest Rewards points up front, plus 1 point per dollar spent, and 2 points per dollar spent on Amtrak tickets. Points are convertible to miles on United Airlines, Continental Airlines, and Midwest Express, on a one for one basis, in 5000 mile increments, with a maximum of 25000 miles per year.

Aer Lingus offers residents of the U.S. and Puerto Rico 1,000 points for applying for and using once its free, no annual fee MasterCard. Plus earn 1 Shamrock Reward point per dollar spent.

MyPoints offers a free MasterCard which gives you 750 MyPoints up front, plus 1 MyPoint for every dollar spent.