jeremyHixon

Gives theme developers and their users a convenient dropdown menu to preview the themes currently installed on the site as well as providing a download link for the one currently selected.
There is an options page in the admin section that allows you to:
<ul>
<li>Choose which themes are available in the select menu</li>
<li>Change the label text for the select menu</li>
<li>Enable/disabled the <a href="https://wordpress.org/plugins/easy-digital-downloads/" rel="ugc">Easy Digital Downloads</a> support.</li>
<li>Enable/disabled the bar globally. If disabled globally, enable on pages/posts.</li>
<li>Enable and disable the default stylesheet</li>
<li>Add custom content to the bar</li>
</ul>

Rational Theme Server

Plugin for theme developers to preview and serve downloads of their themes.

Automattic

Daniel Bachhuber

Alex Mills

Mohammad Jangda

Josh Betz

Nikolay Bachiyski

Thorsten Ott

nickdaugherty

Prasath Nadarajah

A plugin, which helps WordPress developers develop.
This plugin will help you optimize your development environment by making sure that you have all the essential tools and plugins installed.
If you’d like to check out the code and contribute, <a href="https://github.com/Automattic/developer" rel="nofollow ugc">join us on GitHub</a>. Pull requests, issues, and plugin recommendations are more than welcome!
We would like to thank Ejner Galaz for letting us use the <code>developer</code> slug in the WordPress.org plugin repository.

Developer

A plugin, which helps WordPress developers develop.

Rational Theme Server vs Developer