Braintree is great: http://www.braintreepayments.com/ We use them at RapidRollout. They seem to be used by a lot of tech startups. Braintree offers "trans

Braintree is great: http://www.braintreepayments.com/ We use them at RapidRollout. They seem to be used by a lot of tech startups. Braintree offers "transparent" redirects for maximum security. This redirects your users to their site in such a way that they do not ever see Braintree pages like they do with PayPal. The redirect just offers a way to transfer payment data to Braintree servers without going through your servers. They also expose a RESTful API that you can make calls to from your servers (usually via their open-source client libraries). http://www.braintreepayments.com/gateway/api Anyway, looks like you might be able to use AJAX to access the transparent redirect API. See here: http://stackoverflow.com/questions/1776338/signup-form-using-braintree-transparent-redirect But I got that from a quick search only.