Websites, and blogs in particular, are increasingly offering members only sections which might contain extra content for users. Perhaps these members section might require a monthly or once-off payment before you can gain access. So how does one integrate micro-payments into your website?
PayPal is by far the easiest method for accepting payments and this tutorial, PayPal - The PHP Approach, will give you all the information you need. From setting up the MySQL database to acting upon posts from PayPal.
Now what we really need is a nice module for use within WordPress that would automatically create a user once payment has been confirmed (and perhaps optionally expire that user after a certain time period).