ZAP! is a module which makes it fairly straightforward to build WWW-based user interfaces for groups of Z39.50-based information resources. It hides much of the complexity of the underlying protocol and requires mostly an understanding of HTML and some understanding of the Z39.50 database model.
YourPay is a PHP class that can be used to submit WorldPay transactions through a WorldPay account without the very impersonal payment pages provided by the said company. This class will submit the user's credit card details in real-time and return either "Authorise" or "Decline" according to the response.