Core Ruby
A 7-week paid online course covering the material in this tutorial. There are exercises to test and cement our understanding, and we can post our solutions to the private forum. Our instructor, the amazing Victor Goff, is extremely generous with his time and provides lots of useful feedback about how to refactor our code or make it more Ruby-esque.
The best $35 I ever spent - I can't believe how much I've learned, and how fun Victor makes it.