Download Here:  http://drupal.org/project/lm_paypal

Summary

This module provides an interface to PayPal using Instant Payment Notifications (IPN). It currently supports paid memberships (subscriptions), donations (tip jar) and paid adverts (classified ads).

Thoughts

I used this module to help stage a site for someone that required a "paid subscription content" site.  He wants to have content that only his paying customers have access to.  There were several modules, but the lm_paypal seemed to be a more robust / configurable module.  lm_paypal supported auto renewals, different subscription term periods (days, weeks, months), as well as multiple subscriptions.

One thing to note is that you still require a "node access control" mechanism.  lm_paypal provides a mechanism for people who pay to be assigned to a "role".  It is then up to you to use your node access system to give that role (and that role only) access to the paid content.  I chose tac_lite as a simple module to get the job done for my needs. 

The logic I used in creating the paid content was to create a "Subscription01" subscription, a "Subscribers01" role, and a "Subscriptions" taxonomy with a "SubscriptionContent01" taxonomy term.  Using tac_lite you can grant access to the SubscriptionContent01 tagged content to the Subscribers01 role.

lm_paypal also supports paid advertisements and donations, but note this is NOT an ecommerce module.  There are much better modules to meet that need.

This demo site is still a work in progress and I will be sure to update this page with any other tips/tricks I run across.