Not the OP: Google Checkout, followed by Amazon. (Then again, I'm biased ;) Simply because it allows me to pay with something I'll always have handy, my user c

Not the OP: Google Checkout, followed by Amazon. (Then again, I'm biased ;) Simply because it allows me to pay with something I'll always have handy, my user credentials. At any given point, I might or might not have a credit card close by. (Yes, I read HN in bed :)