It has to be the scikit-learn documentation (<a href="http://scikit-learn.org/" rel="nofollow">http://scikit-learn.org/</a>). Not only its great in terms of proper code documentations with a ton of examples, but it also explains the theory behind each algorithm. You can literally learn Machine Learning just by reading the docs
Any discussion on documentation is incomplete without mentioning Django<p><a href="https://docs.djangoproject.com/en/2.0/" rel="nofollow">https://docs.djangoproject.com/en/2.0/</a>
MDN because it's exhaustive <a href="https://developer.mozilla.org/en-US/" rel="nofollow">https://developer.mozilla.org/en-US/</a><p>Jekyll because it's beautiful and the user can read all the pages at once with the previous/next buttons (at the bottom) <a href="https://jekyllrb.com/docs/home/" rel="nofollow">https://jekyllrb.com/docs/home/</a><p>Node.js because they propose a single page version and it makes search easier <a href="https://nodejs.org/dist/latest-v10.x/docs/api/all.html" rel="nofollow">https://nodejs.org/dist/latest-v10.x/docs/api/all.html</a>
I learned a lot from the SQLite documentation. It's not only very thorough, but it's full of insightful bits of information that is not strictly necessary but which gives a deeper understanding of the engine.<p>It was also the first time I encountered the flow diagram type of syntax explanation which I found to be a fantastic way to grasp the details of each command. Eg <a href="https://sqlite.org/lang_createtable.html" rel="nofollow">https://sqlite.org/lang_createtable.html</a>.<p><a href="https://sqlite.org/docs.html" rel="nofollow">https://sqlite.org/docs.html</a>
ZeroMQ stands out for me.
<a href="http://zguide.zeromq.org/page:all" rel="nofollow">http://zguide.zeromq.org/page:all</a>
PostgreSQL's documentation to me is a reference.<p>Complex concepts are told in a very simple and concise fashion. There is just the right amount of text for what is told, it does not make you feel dumb and instead invites you to dig deeper in a very welcoming manner.
Re-frame for clojurescript. Worth reading even if you're not using cljs but are involved in front-end development.<p><a href="https://github.com/Day8/re-frame/blob/master/docs/README.md" rel="nofollow">https://github.com/Day8/re-frame/blob/master/docs/README.md</a>
The TeXbook, and the Exim spec.<p>The thing the latter gets right is that, as well as the usual long list of options with an explanation of what their effects are, it also describes in full detail what the program actually does, rather than leaving you to deduce it from the options.<p>So each option is normally described twice: once in an alphabetical list, and once where the operation it affects is described.
vim, emacs, postgres, zsh, bash, urxvt, systemd, pacman<p>EDIT: It all depends on how you set the bar, though. There are plenty of projects whose entire documentation is a README with a few examples.<p>Also, what's "best", documentation that greatly explains a horrible, unintuitive interface of a program or one that hardly needs to exist because the use of the program is so intuitive, you don't need documentation? Greater effort was spent in the former, but you understand the program better in the latter.
I love <a href="https://redis.io/documentation" rel="nofollow">https://redis.io/documentation</a>. It has a great UI too.
Django, the Python-based web framework, has fantastic docs too: <a href="https://docs.djangoproject.com" rel="nofollow">https://docs.djangoproject.com</a>
The node-postgres docs are very nice. <a href="https://node-postgres.com/" rel="nofollow">https://node-postgres.com/</a><p>Gives you examples right off the bat to get started, is organized well so it's easy to dive deeper, and the author includes some conventions for incorporating the module into your app.
QT wasn't so bad as far as I remember.<p>But as jolmg pointed out, some projects are just simple readme and that is more than enough. Love those. But the total opposite is also common, a wall of text that is meaningless and in the end, you have to go through the source code to get some answers...
Erlang - <a href="https://www.erlang.org/docs" rel="nofollow">https://www.erlang.org/docs</a><p>The best three entries are
* Learn - <a href="http://erlang.org/doc/reference_manual/users_guide.html" rel="nofollow">http://erlang.org/doc/reference_manual/users_guide.html</a>
* Use - <a href="http://erlang.org/doc/search/" rel="nofollow">http://erlang.org/doc/search/</a>
* Go deep - <a href="http://erlang.org/doc/efficiency_guide/users_guide.html" rel="nofollow">http://erlang.org/doc/efficiency_guide/users_guide.html</a>
I would go with python-requests <a href="http://docs.python-requests.org/en/master/" rel="nofollow">http://docs.python-requests.org/en/master/</a>
<a href="https://docs.saltstack.com/en/latest/topics/development/index.html" rel="nofollow">https://docs.saltstack.com/en/latest/topics/development/inde...</a><p>I found some bugs and I wanted to fix them. I've done a little python in the past but I'm not entirely up to speed on the whole python ecosystem. This documentation was exceptional and allowed me to get my bugs fixed, some unit tests written and PR's merged.
I've always admired Agilent's Programmer's Reference for the ESA series electronic spectrum analyzers
<a href="http://literature.cdn.keysight.com/litweb/pdf/E4401-90507.pdf" rel="nofollow">http://literature.cdn.keysight.com/litweb/pdf/E4401-90507.pd...</a>
I really like the elasticsearch docs. They seem to cover everything, it's easy to find what you're looking for, and they contain a lot of detail! the feature where you can switch ES version without leaving the page you're on is a nice touch too :)
It's gotta be emacs for me. C-h o, and helm-apropos make it super easy to investigate anything in the system. And the help pages link back to the source code (though this isn't unique to emacs) The online docs aren't bad either.
Probably the Gentoo Linux documentation. Not sure how it looks like today, but back in 2005 when I started using Gentoo it helped me a lot because not only was comprehensive but also deep enough albeit clear.
I really like the Org mode manual (<a href="https://orgmode.org/manual/" rel="nofollow">https://orgmode.org/manual/</a>)
nobody know shoes by _why<p>I would say it's pretty terrible at providing a reference for a new GUI system in ruby, but it's also the most fun I've had reading docs
PostgreSQL's is very concise, clear, to the point, but still very detailed. Has examples! <a href="https://www.postgresql.org/docs/10/static/index.html" rel="nofollow">https://www.postgresql.org/docs/10/static/index.html</a>