One of the first really good Ruby activities I did was Ruby Koans. This is a highly recommended learning tool from beginners to master level Rubyists. Here is the rundown:

What is it? A super cool way of learning Ruby by doing thought provoking exercises seasoned with a dash of TDD.

Who is it for? You would need to be familiar with the command line and have at least some programming background. Some familiarity with TDD will help. No Ruby knowledge is required.

Breadth of Instruction: Not every single element of Ruby is covered but most basic things like variable types, iteration, hashes, blocks, exception handling and a few advanced things like Java interop. Quite a bit more than just the basics.

Depth of instruction: This is skill building material. You have to edit files. Do projects on your own. You can’t just jam through the materials and expect to get it. You are going to have to thing a bit on this one. Although I’m far from a ruby master, I suspect there is enough depth in this material that even a master level folk is going to get a couple of gems out of this.

Value: Off the chart. Costs nothing but time.

Cost: Free

Setup: Ruby > 1.8 and text editor

Recommendation: Download the koans and dig in.

Where: Ruby Koans