Here are the slides for the Ruby Dependencies, Notifications, and Adjustments talk I've recently given at DCRUG and Bmore On Rails:
The talk discusses the object peer stereotype concept introduced in the book Growing Object Oriented Software, Guided by Tests. I also mention Jim Weirich's post about Ruby Dependency Injection.
I used the experimental terminal keynote software to make the slides. It was pretty fun writing my slides in Ruby, and I'd definitely recommend using it for code-heavy talks like this one. But if you need diagrams or something more visually-stimulating I'd recommend sticking with GUI-based software.