Day job: None really, I'm a "high school student" (I'm in 13th grade, which would be Freshman year in college in the US).
What is your language of choice: Ruby. I'm looking at other "secondary" languages, such as
Open Source contributions: Mostly a bug report, maybe a fix here and there. There's also my own project, Defender.
How do you use GitHub: I use it to discover new libraries and programming goodies. When I needed an IMAP library for Objective-C, GitHub was the first place I looked. I also host everything I make of programming things (and a bit more, like dotfiles), as soon as it reaches a stage where there's some "runnable" code (even if it just throws an exception), I push it to GitHub.