Brilliant work — my only suggestion would be to add a few more sections for "modern" tools like Git, Mercurial, Nginx, Redis, OpenVPN, Python easy_install, Ruby gems, LXC, etc.
And perhaps also a section on ancient, but widely used, systems like autotools — even something as simple as ./configure --prefix would be useful to have known...
Hmz, I wonder if the author is aware of this thread on HN?
Perfections seems to be the enemy of good.
Actually I really like site format as ~50 page reference seems to be really useful, or something that you could take on a long car trip and casually look into.
I think that maybe programming and Make examples were unnecessary -- they don't really give any idea about what to do with the language and don't present any paradigms or quirks that you might need and there are much better short tutorials on that topic out there. All in all, this wouldn't save you if you got to write something in C++, but this would definitely help if you need to remember some unix command that's just slipped your mind.
Though they might have included stuff for LVM to 'file system' section, LVM commands are more or less intuitive as they are.
It's a fake terminal but it's surprisingly fully functional (lots of commands work, tab autocompletion, etc.)