A burgeoning but vibrant Ruby developer community meets up once a month in the Tel-Aviv area, thanks to the efforts of Roy Osherove and some leading Ruby developers. I had the honor to conduct a talk this time (December), and my subject was metaprogramming from scratch. Since this is normally considered an advanced subject, I took the approach to explain core concepts through runnable code snippets that the participants could feed instantly into an interactive shell and see the results. The main exercise was a custom implementation of the Ruby built-in method "attr_accessor" using metaprogramming techniques.
P.S. Follow me on Twitter.