E-commerce railers,
There have been many questions on this list by myself and others about how to handle storing customer credit card information in a secure way. This normally is a requirement of web apps that bill on a subscription basis (ex. Basecamp).
I recently had to tackle this problem and chose to use a payment gateway named TrustCommerce (http://www.trustcommerce.com). They have a product named Citadel (Healthcare Payment Management | Payment Processing Security) that allows you to store customer credit card information securely on their servers and then bill that customer monthly, quartery, etc. You can create customer profiles through their website or API.
I wrote the TrustCommerce subscription plugin as a simple interface to create, edit, delete, and query subscriptions using the TrustCommerce Citadel API.
You can get the plugin here: http://svn.depixelate.com/plugins/trustcommerce_subscription/
You can read about it here: http://depixelate.com/2006/10/20/trustcommerce-subscription-plugin-released
The plugin is currently being used in production here: http://www.servicesidekick.com
I hope this can be of use to others.
Any feedback is appreciated.
-- Zack Chandler http://depixelate.com