Some games are too young to own a credit card so options for purchasing games from the PlayStation Store is limited. Well, not so much anymore. In early 2008, PlayStation Network Cards will be available to purchase from retail stores in a number of denominations. The cards can be redeemed on the PS3 PlayStation Store and PlayStation Store for PC.
The exact denominations have not been revealed yet, but look out for more details when the cards are available. The PlayStation Network Cards should be coming to Europe soon, but a release date has not been revealed.