I'm always on the lookout for tools that help kids -- well, all folks really -- how to code. So add this to the list:
Hackety-Hack is an app designed to teach complete beginners how to program in Ruby. The step-by-step guide walks you through some on the basics of the Ruby language, as well as some basic Shoes, a Ruby toolkit that lets you build graphical interfaces. In addition to lessons, there are other code samples, and you can upload your code to the website where there's also a Q&A section. It's all designed to get you ready to build your own apps.
Hackety-Hack is available for Windows, Mac and Linux and is free and open source.