Ryan, I'd like to help out with this too. It's something we'll need completed in the next couple months.

I think maybe a generic recurring payments module "Recurring Payments" and then maybe some extensibility - in other words a "Recurring Payments - Paypal" and "Recurring Payments - Credit card/ A.net" that way people can turn on / off different options.

The main thing is that the Recurring Payments should be generic enough that a person can use any payment method that's on a site, but I think it's probably easier to create an API which then developers can contribute modules for other payment methods (or simply add a new hook to an existing payment method module such as Payflow, PayPal WPS, etc).

If you need any help let me know, we're using primarily PayPal and Authorize also.