user84: Currently; when I start a new Arduino project with some new hardware, the first thing I do is to look for 3rd-party libraries that bring Arduino support for this hardware.
The first places I look are:

The Arduino Playground
GitHub
Google

Generally I find either no support library or several different libraries (it's quite rare to find only one) in different locations with different levels of documentation, different levels of testing...
Once I have found the library I need (sometimes I need to try several), I download it to my Arduino libraries folder, I use it and I forget it.
I find this process cumbersome:

manual search with different possible options, not always well documented
manual download and install to Arduino libraries
no version control in the process (all versions of a library have the same name and thus cannot coexist in the Arduino library folder).

I wish there was a central repository with all available libraries for arduino, with:

description (supported hardware, supported boards)
source code
documentation
versions

And a tool (Arduino IDE or external) to access this repository at project build time.
A kind of maven for Arduino in fact.
I have seen several discussions once took place on Arduino forum, but it seems they led nowhere:

Arduino Libraries Census and Repository
Arduino Library downloader
Arduino Library downloader (2)

Are there other options, that are made it to something usable (from the community or individuals, why not)?

user86: There is none. Unfortunately, you will have to manually search for each library you are interested in.
If you are interested in creating such a central repository, while it would be awesome, this is not the correct forum in which to do it.

user7508: If you want to create such a registry yourself, you may want to take a
look at npm, the package manager of Node.js, which is
open-source and very similar in scope to want you describe. Npm is both:

a central registry with metadata about each library:

name, description, keywords, homepage, author, contributors
version number, in principle complying with semantic versioning
URL of source repository (svn, git, github, gitlab, bitbucket...)
compatibility information (in this case it's about the versions of Node)
license
dependencies


a command-line tool for:

searching the registry
downloading and installing packages, recursively following their
dependencies
publishing and updating your own packages on the registry.



See for example the page of a popular library, and the JSON
file holding its metadata.

user37: The Arduino Playground LibraryList and the standard library list appear to be the official pages for that.

user24470: Since this question was first asked, there is now the Arduino Library Manager, built into the Arduino IDE. There you can search for and install libraries.
There is information about how the library manager works here:
https://github.com/arduino/Arduino/wiki/Library-Manager-FAQ
There isn't however an official website listing the libraries, so I recently created this unofficial site, based on the same data in the Arduino Library Manager:
http://www.arduinolibraries.info/

84: <p>Currently; when I start a new Arduino project with some new hardware, the first thing I do is to look for 3rd-party libraries that bring Arduino support for this hardware.</p>

<p>The first places I look are:</p>

<ul>
<li><a href="http://playground.arduino.cc/">The Arduino Playground</a></li>
<li><a href="https://github.com/">GitHub</a></li>
<li><a href="http://www.google.com">Google</a></li>
</ul>

<p>Generally I find either no support library or several different libraries (it's quite rare to find only one) in different locations with different levels of documentation, different levels of testing...</p>

<p>Once I have found the library I need (sometimes I need to try several), I download it to my Arduino libraries folder, I use it and I forget it.</p>

<p>I find this process cumbersome:</p>

<ul>
<li>manual search with different possible options, not always well documented</li>
<li>manual download and install to Arduino libraries</li>
<li>no version control in the process (all versions of a library have the same name and thus cannot coexist in the Arduino library folder).</li>
</ul>

<p>I wish there was a central repository with all available libraries for arduino, with:</p>

<ul>
<li>description (supported hardware, supported boards)</li>
<li>source code</li>
<li>documentation</li>
<li>versions</li>
</ul>

<p>And a tool (Arduino IDE or external) to access this repository at project build time.</p>

<p>A kind of <a href="http://maven.apache.org">maven</a> for Arduino in fact.</p>

<p>I have seen several discussions once took place on Arduino forum, but it seems they led nowhere:</p>

<ul>
<li><a href="http://forum.arduino.cc/index.php?topic=73531.0">Arduino Libraries Census and Repository</a></li>
<li><a href="http://forum.arduino.cc/index.php/topic,1460.0.html">Arduino Library downloader</a></li>
<li><a href="http://forum.arduino.cc/index.php/topic,63215.0.html">Arduino Library downloader (2)</a></li>
</ul>

<p>Are there other options, that are made it to something usable (from the community or individuals, why not)?</p>
 86: <p>There is none. Unfortunately, you will have to manually search for each library you are interested in.</p>

<p>If you are interested in creating such a central repository, while it would be awesome, this is not the correct forum in which to do it.</p>
 7508: <p>If you want to create such a registry yourself, you may want to take a
look at <a href="https://www.npmjs.com/" rel="nofollow noreferrer">npm</a>, the package manager of <a href="https://nodejs.org/en/" rel="nofollow noreferrer">Node.js</a>, which is
open-source and very similar in scope to want you describe. Npm is both:</p>
<ol>
<li>a central registry with metadata about each library:
<ul>
<li>name, description, keywords, homepage, author, contributors</li>
<li>version number, in principle complying with <a href="http://semver.org/" rel="nofollow noreferrer">semantic versioning</a></li>
<li>URL of source repository (svn, git, github, gitlab, bitbucket...)</li>
<li>compatibility information (in this case it's about the versions of Node)</li>
<li>license</li>
<li>dependencies</li>
</ul>
</li>
<li>a command-line tool for:
<ul>
<li>searching the registry</li>
<li>downloading and installing packages, recursively following their
dependencies</li>
<li>publishing and updating your own packages on the registry.</li>
</ul>
</li>
</ol>
<p>See for example the page of a <a href="https://www.npmjs.com/package/express" rel="nofollow noreferrer">popular library</a>, and the <a href="https://github.com/expressjs/express/blob/master/package.json" rel="nofollow noreferrer">JSON
file</a> holding its metadata.</p>
 37: <p>The <a href="http://playground.arduino.cc/Main/LibraryList" rel="nofollow">Arduino Playground LibraryList</a> and the <a href="http://arduino.cc/en/Reference/Libraries" rel="nofollow">standard library list</a> appear to be the official pages for that.</p>
 24470: <p>Since this question was first asked, there is now the Arduino Library Manager, built into the Arduino IDE. There you can search for and install libraries.</p>

<p>There is information about how the library manager works here:
<a href="https://github.com/arduino/Arduino/wiki/Library-Manager-FAQ" rel="noreferrer">https://github.com/arduino/Arduino/wiki/Library-Manager-FAQ</a></p>

<p>There isn't however an official website listing the libraries, so I recently created this unofficial site, based on the same data in the Arduino Library Manager:</p>

<p><a href="http://www.arduinolibraries.info/" rel="noreferrer">http://www.arduinolibraries.info/</a></p>
