Authorizenet
Authorize.Net offers secure, scalable solutions that enable merchants to process unlimited transactions from anywhere in the world. Our solutions support any business model -- Internet, broadband, wireless, call center and retail -- and come with free technical support.
authorizenet.com/

Datacash
DataCash is a UK market leader in outsourced real-time online processing and fraud screening of Credit Cards and Debit Cards + Paperless Direct Debit & Direct Credit. DataCash is suitable for merchants transacting through the Internet, call centres, iDTV, m-commerce and high street point of sale (POS) terminals.
datacash.com/

iBill
If you're selling products and/or services on the Internet, iBill has a turnkey e-commerce solution that's designed just for you.
ibill.com

Stormpay
StormPay Inc. is an online payment system, which allows anyone with an email address to send or receive payments. Founded in October, 2002, StormPay Inc. has quickly become an Internet leader in online payment processing by offering customers and vendors alike, a safe and secure method to do financial transactions across the Internet, while reducing the risk of exposing your financial information.
stormpayinfo.com/

Worldpay
WorldPay enable thousands of businesses to accept payments on the internet, by phone, fax or mail. Credit and debit cards, bank transfers, instalments - even mobile payments. In any language and most currencies. All through one merchant account, one payment processing system. Part of the second biggest bank in Europe, we're elemental to e-commerce.
worldpay.com