Learn Ruby with the Neo Ruby Koans

The very first test case is simple - true versus false. Then it progressively built up from there. Data types, flow control, object hierarchy, the works. While this covers much of the same ground as the Codecademy course I took a few days ago, the presentation and the format kept me engaged in a way the Codecademy course did not.
One reason was that it's possible to "fast forward" through sections I understood: The test cases are all there in Ruby source files. So once I understood the concept covered by one test case, I can continue editing the similar test cases and have them all passing in one batch instead of one case at a time. In contrast to something like Codecademy where, even if I understood the concept, I still had click through the pages one at a time.
Bonus: after I finish the lessons, I have a bunch of Ruby files exercising various Ruby concepts that I can go back and look at for reference. It is much faster to scan through a Ruby file than it is to click through a Codecademy lesson.
This Ruby Koans approach to learning Ruby might not work with everybody, but I loved it.