Hi Patrick,
Is it more "Intro to programming", "Intro to Ruby for people that know at least basics of programming" or "How to do cool things with Ruby like deploy an application to the cloud?"
I could give a 15-minutes demo on creating a new Rails application and deploying it to Heroku, giving the names of the technologies used along the way. I find that one of the hardest things with a new environment is getting things to work the first time. Once the project is set up, doing incremental changes is something people can experiment with on their own.
Julien