Paypal Subscriptions

Dan,

It is possible to do recurring billing with paypal and activemerchant
if you are have a Website Payments Pro Payflow Edition account w/
recurring billing enabled. This type of account isn't a standard
offering on the paypal sites. I had to call a sales rep and
specifically request this to get a special "token" I could use to
apply. Activemerchant has built in support for doing recurring billing
via Payflow using the Payflow gateway (which uses Paypal's XMLPay
apis).

- Robin Curry

This is a complicated topic, especially with Paypal. They're going
through a branding transition, so it may not make sense right away. I
wrote up how I'm handling this in Lighthouse:

http://activereload.net/2007/5/17/dealing-with-subscription-payments
http://activereload.net/2007/6/6/follow-up-to-subscriptions