Whenever I’m learning a new programming language, I find it helpful to keep notes on what I learn. Ruby is no exception, except this is the first time I have tried compiling these notes into more of a tutorial.
You can see the first draft of it (or the Alpha version), over here.
Its style is based on the assumption that you can always find out about the practical usage of the language, its classes, functions, and methods, later. Lightning Tutorials (yes, I intend to write more) attempt to teach only the absolute essential parts of the language, its syntax, idioms, features, and gotchas. Because they do not explain anything but the most fundamental parts of the language, they can be very concise. However, you must already be a relatively competent programmer to understand them. I don’t explain what terms such as “instance variables” or “classes” mean, as they are not intended to be an introduction to programming, but rather a quickstart guide for experienced programmers who wish to get up and running on a new language quickly. After all, you can always read the language docs later.