When I am out and about and I have some idle time, how could I use this to further my learning in python, html, css, javascript, sql, ruby, rails, etc?

Any apps or guides done specifically for this? The problem with just reading a programming ebook is that it generally requires writing out the code, so I have to bookmark pages and go back to those when at a computer, which doesn't work so well, so it would be better if there was just some stuff that was suited to doing while out.