Ask HN: Merchant Accounts & Payment Processors in the US?

I just read this article - http://blog.boxedice.com/2009/05/20/taking-payments-online-merchant-account-payment-processor-fees/ - but it is strictly for the UK. It is quite insightful, and detailed, but doesn't make sense for me because I don't live in the UK.

Does anyone know of a similar write-up for the US and other international countries?

Thanks.