Authorize.net - Payment gateway enables internet merchants to accept online payments via credit card and e-check.
Fattmerchant - Subscription-based credit card payment processing platform
Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.
Helcim - Helcim is a feature-rich online solution that facilitates payment procedures by enabling a range of industries as well as businesses to accommodate several payment options.
PayPal - PayPal is the faster, safer way to pay online without sharing financial details, send and receive money or accept credit and debit cards as a seller
Gravity Payments - Gravity Payments is a comprehensive credit card processing platform that helps you get paid any way you want, with the least amount of hassle.