USAePay is a payment gateway. This gateway is extremely versatile and robust and allows merchants to accept credit, debit and ACH payments.
Authorize.NET is a payment gateway used by merchants to accept credit card and ACH payments.
NCR is a Point of Sale (POS) company based in the US. Their POS is a great fit for QSR, Retail and full service restaurants.
First Data is the payment processor based in Atlanta, GA. They currently process an estimated 45% of all US credit and debit card transactions.
Verifone is a hardware company that supplies credit card terminals. More than 7 Billion transactions are processed on a Verifone terminal. These terminals can integrate to a POS, tether to a POS or be used as a stand alone terminal.