I use
www.magentocommerce.com, which is powerful, but it may take you a little bit of time to figure out where everything is to skin it. I assume its like that with everything though.
It enables you to use authorize.net. paypal, saved credit card number, and some other options i think. They have free and paid modules you can get for other processors via
www.magentoconnect.com, They also have a tutorial if you are good with code on how to write your own payment processor module.
I am assuming this has to do with porn or I would have recommended
www.simplecartjs.com. It is simple and doesn't use a database and lets you insert products via div tags i think, but i am pretty sure it only works with paypal or google checkout.
Best of luck