Last spring I spoke at Ruby Manor 4 about game development with Ruby. It's a bit weird choice for game development, but I'm totally in love with Gosu (a minimalistic 2D game development library).
And finally the video is available!
Here are the slides:
Note regarding the last question asked by the audience, about Gosu working with RubyMotion. I screwed up :) We were discussing this afterwards in the pub, but there are two main reasons: one is that mobile phones use a different OpenGL version (OpenGL ES) than desktop. The other is that touch events are not included in the desktop version. You can see a discussion about this at Gosu's forum.