Everyone has their own ways of learning. I know that some people might not want a full subscription with so many projects, but might want to work one project at a time. If that is your learning preference, Individual Lessons are for you.
Most of the lessons, beyond the Beginning Projects category, have Individual Lessons that can be purchased separately. If a lesson is available for purchase, the Introduction page for the lesson features a "Buy This Lesson" button prominently in the upper right corner. Press that button to buy. All lessons are sold through a marketplace that accepts credit card payments and handles all of the download process for you.
You can find a full list of all Individual Lessons via the link in the footer of the website, or through this link.