Tailfish Solutions recommends the following Card Processing Gateways

Encore Payment SystemsTailfish can provide assistance with the application process for an Encore Payment Gateway.
Stripe.com
Authorize.NET
PayPal Payments Pro

 
 

Below you will find a complete list of supported gateways.

2Checkout
Alipay
AlliedWallet
ANZ eGate
Authipay
BeanStream
BluePay
Braintree
CardStream
CCAvenue
Certitrade
ClickandBuy
CyberSource
DataCash
DIBS
Dwolla
Elavon
eWay
FirstData Merchant Solutions
IcePay
InfusionSoft 
InspireCommerce
Intuit Payments
iPay88
Klarna
MerchantWarrior
MOIP
myGate
NAB Transact
NetBanx
Netbilling Payment Gateway
NovalNet
Ogone
PayEx
PayJunction
PayLeap
Payment Express
PayMill
PayPal Express
PayPal Standard
PayPal Advanced
Paysius
PayTrace
PayTrail
PayU
PayWay API
PayWayNET
Payza (AlertPay)
PIN Payments
PSI Gate
RealEx
RedSys
Sage Payment Solutions
SagePay Direct
SecureNet
Simplify Commerce
Sisow
Skrill (moneybookers)
TotalWeb Solutions
TrustCommerce
USAePay
VirtualCardServices
WePay
Wirecard
WorldPay