swergroup

This plugin let plugin and theme authors to display their work in their main WordPress. It provides some helpers:
<ul>
<li>two custom post types: plugins and themes</li>
<li>SEO-friendly URLs</li>
<li>fetch (and cache in transient) plugin/theme info from the latest readme.txt file</li>
<li>fetch (and cache in transient) rating / support / downloads info</li>
<li>plugin info from readme file as custom post metadata</li>
</ul>
Planned in the next release:
<ul>
<li>widgets with plugin info</li>
<li>shortcodes</li>
</ul>

Developer Showcase

Plugin/theme showcase plugin for WordPress plugin/theme authors and developers.

nextiteration

The Style Switcher plugin allows developers to offer clients a set of options for quickly swapping out and viewing different style options, from the front-end WordPress UI. Clients don\’t need to know anything about css or even WordPress admin options.
For example, if you would like to test a few different color options for headers, the plugin will allow you to set appropriate options, and the client can toggle between them, seeing changes live on the page.

Style Switcher

Let clients test simple style changes on the front end, to help make final decisions.

Developer Showcase vs Style Switcher