Ask HN: How did you get involved in your first open source projects

I reading through pragprogs Metaprogramming in Ruby. In order to learn better by applying knowledge from the book to real world projects, I want to get involved with some cool Ruby (Metaprogram) or Rails projects on Github. However, many of the projects I've came across are not just "starters", they require a lot of domain knowledge.

I'm wondering how did you some of you get involved in your first open source project on github and what projects are you involved in?