Foundations of Active Record and Action Pack libraries, otherwise known as the basis for the Model View Controller framework that Rails is built on. Which they probably could have said more clearly.
One of the best examples of context based learning I've seen, this free online textbook teaches Rails concepts by having students build a professional quality web application.
An introduction to front end web development put into context using great examples, assignments, and an overarching professional demonstration.
Introduces students to the basics of Ruby on Rails, through an overview of Ruby syntax and a rushed Rails template project.