Recently, we added credit card processing to inventables.com. This makes it possible for Vendors that promote products on our website to buy sales leads when potential customers submit an inquiry about their product. We have a small software development team and we wanted the functionality fast. Some quick googling showed that there are many solutions out there for large payment processing sites like Paypal or Authorize.net. However, we were using a payment processor that these solutions didn't support.
We use open source software and think it's important to contribute to the open source community. If you're interested in reading a more technical description of how we accomplished this, take a look at this post. If you'd like to use the code on your own site you can. We released an open source library on GitHub.