Helpful PayPal IPN notes

Just a quick note today that in creating my "Hide Your Desktop" application, I don't know if I would have gotten through all the PayPal "Instant Payment Notification" (IPN) integration work without great articles like this one from

While that article is a little terse in spots, it's also very helpful, in particular in guiding you through the maze that is PayPal. So, many thanks to Simon Strandgaard for those PayPal IPN notes.