I think a paywall just hides a site's content from nonsubscribers so it's just a euphemism for a subscription site. As for micropayments, yes I think a lot of us are familiar with that technology - paypal and amazon fps developer docs ought to be enough to get you started. What specifically are you trying to accomplish?
Thanks. Will read the documentation. I'm interested in requiring a user's micropayment prior to viewing each piece of content.