For anyone without a credit or debit card, adding money to an iTunes or App Store account usually means picking up a gift card from a retail store. iTunes Pass, which originally launched its test run in Japan, is now available in several additional regions and offers another way to buy content from Apple's digital marketplaces.
With iTunes Pass, you can go into an Apple Store and load up your iTunes/App Store account with funds by bringing up the iTunes Pass card in Passbook and having an Apple representative scan it. The money can then be used immediately. At the moment, it appears the new option is live in the U.S., United Kingdom, Canada, Germany, and is likely rolling out to others as well, though Apple hasn't yet revealed a full list of supported regions.
It's a feature most of us will never really care about, but for parents who prefer to pre-pay their kids' iTunes accounts rather than link their accounts to a credit card, it could be a fantastic tool. Of course, the fact that it will also increase foot traffic to Apple retail locations wouldn't hurt either, which I'm sure is something Apple has thought about as well.