In regards to the credit card payment system, I just found this:
http://www.thesitewizard.com/archive/creditcards.shtml
explains everything so far said and more.
edit:
Dug around in Paypal for merchants too... Seems to be more what I'm looking for. As SonicSam showed, it gives the customer the ability to pay by credit card without the need to register or login into an account
(they still can though, and that on its turn gives the ability to pay via their PayPal account). Which is exactly what I'm looking for. Now to find the same thing but where they also can pay with wire/bank transfer
/ 
