I've just finished working through the RubyKoans, and I've got to say
what a fantastic way of learning about Ruby they are!
I like to think I'm fairly familiar with the Ruby documentation, but I
learnt a couple of things going through them. Very informative. I
shall be recommending them left-right-and-centre to anyone asking "how
do I start with Rails".
Big thanks to the authors *applauds*