This may be a silly question, but not having got into the kindle craze myself I'm wondering if someone can tell me the best way to buy a gift card to give to someone for christmas for a kindle bought in an NZ shop?  Do I just go to amazon.com gift cards section and buy one there and they'll be able to use that?  I assume it's in USD then?  Or is there a better way and do I need to worry about regional pricing or anything like that?