Authorize.net is the worlds largest credit card processing system and primarily a U.S. based gateway. They have a very nice user interface for you to manage your transactions, refunds, and outside-the-onlinestore transactions through their virtual terminal.
PayPal is an obvious standard for 3rd party processors. We have integrated with their standard payment system and this allows customers on your site to be directed to paypal and pay on paypals website. This provides a multitude of currency and country support.
FirstData also provides a variety of customer solutions, from Americs to European customers. Check with an agent and their website to see if you qualify for a merchant account.
Chronopay provides services for many European customers if they wish to process their money in non-USD dollars, however, it will also do USD... which makes them a very versatile choice.
Eway is a new integration that provides support for Australian and New Zealand dollars and currency.
VersaPay is an integration for Canadian customers that allows transactions in canadian currency and also in U.S. dollars if needed.
PaymentExpress is a popular southeast asian processor and european processing system. A good choice for a variety of countries, so check their site for availability of a merchant account in your area.
PayPoint is a popular european provider and is integrated with their full API solution, which allows for payments on your website.
Of course with all services, there are transaction fees, just like in a real brick and mortar store. We can help you decide which option is best for you by calling and discussing your individual needs.