Open Source contribution (if any): I've contributed to vimerl.
Tell me about your experience with Ruby/Rails: I use ruby and sinatra for side projects. I've contributed to MrT (command-line competion). I tend to do round-robin between ruby and python for scripting. I'm very often using ruby in my projects, even if it's not directly: git custom workflows, presentations (showoff), configuration management (puppet, vagrant), email client (vmail), etc.
How do you use GitHub: I use it all the time. I use it to follow projects I'm interested in or to find new projects. I put my side projects and presentations on github. And I also use it at work with private repositories (pull requests, code review, issues, etc.). I couldn't live without it.