For the PlayBook's App World, where you buy apps for the PlayBook, I linked my PayPal account. It is not the greatest solution, but it is safer, I think, then linking my credit card.
I like iTunes solution. In a misconception, you don't need a credit card to set up or use an iTunes account. For setup, you need to just skip the input of a credit card number. What I like to use are iTunes gift cards. At times, stores will sell iTunes gift card for 20% off. For $80, you could get a $100 card. But I don't use that much. What I do is turn in my loose change at a CoinStar machine. They have an iTunes option, in which your coins deposited are turned into an iTunes gift card and the fees are paid by iTunes. It's a good deal.
CoinStar also has an option for Amazon, but I hate Amazon. They seem to always required a credit card. They do sell apps for Android, but I think you need a credit card even if you use a gift card.
With Google's Play Store, they now offer you the use of gift card. The only problem, I can't find one. For the past 2 days, I have visited 20 retail outlets and could not find a Play Store gift card. I was not really shopping for them, but I would look at every store l was at.
I like Apple's approach to their app sales a lot. I also like that I can gift an app with them. Of course, the person receiving an app must have an iOS device.
