We have integrated to Credit Card Company API in the past. However, with PCI compliance much more strick it requires some serious thought. The Webservice calls themselves are quite simple and most merchant providers have external APIs for you to use.

There is no one size fits all solution as it really depends on you business model and what data you are collecting as part of the payment process.

If you want you can PM me for more help.

Kind regards

Do you have a card processor picked out? The exact method would depend on the processor. Some have OLE controls which would make it very easy.

Hi Winthor,

Paypal exposes a very simple API.

You can issue a payment using query strings to specify merchant ID, description, amount and currency. 

For example (sandbox lets you test without actually performing the transaction):

https://www.sandbox.paypal.com/cgi-bin/webscr?cmd=_xclick&business=44K2YPE4VLFJC&item_name=myItem&amount=100.00¤cy_code=USD

My 2 cents,

Best,

Marco