There are many, many and more many Credit Card Gateways out there that let retailers accept credit cards. They are all terribly expensive. Signup fees, closing fees, monthly fees, per sale fees... it's brutal. A popular one is 2checkout.com because they have a $50 setup, then 5.5% per sale there-after. This means that once you fork over the $50, your good to go for years to come. However, that 5,5% is a real killer.
Personally, I signed with LinkPoint.com because they had no extraneous fees. While It has a $25/mo fee, the 2.3% per sale is quite nice compared to what else I saw out there. Customer Service was smart and knew their stuff, but were foreign, and didn't want to be bothered with me, it seemed. Two calls, both pointed me to the help docs.
The break between these two seems to be, that if you plan to sell 1-5 things a month, go with 2checkout.com. But if you expect to do 2+ sales a week, go with LinkPoint.com and if you missed everything else I have been complaining about for the past month, don't EVER use PayPal.