The other tutorial that I created for Google I/O this year just went live. In "Using Ruby on Rails and YouTube for Education", I explain that Ruby on Rails, YouTube, education, and TDD are like a peanut butter, honey, and banana sandwich! I'm particularly proud of the section that teaches you how to do test-driven development with RESTful web services, including a "live" (for some definition of live) coding session. Enjoy!
Ad maiorem Dei gloriam inque hominum salutem.