knuten

This plugin let you add a shortcode with two different image sources one too a normal sized image and one for retina. The plugin will then load the right image depending on if it’s a retina display or not. 
For more info and how to use it.
<h3>A brief Markdown Example</h3>
<pre><code>[retina normal="path-to-normal-image" retina="path-to-retina-image" width="image-width" height="image-height" /]
</code></pre>

Retina for WP

This plugin let you add a shortcode with two different image sources one too a normal sized image and one for retina.

nackle2k10

Portfolio
If your theme supports portfolio, the Toolkit adds a Portfolio custom post type. Once enabled, you will see a Portfolio Post type in the menu item, which you can use to create your portfolio.
Quiz
If your theme supports quiz post type, the Toolkit adds quiz support. Once enabled, you will be provided with a simple quiz tools.
Poll
If your theme supports poll post type, the Toolkit adds poll support. Once enabled, you will be provided with a simple polling features.
Toolkit Widgets
The Toolkit adds Twitter, Flickr, Dribbble, Video (Support Self Hosted and Third Party Hosted) and more than 20 Retina Ready social media icons to your theme.
Toolkit Shortcodes
The Toolkit also adds Google Maps, Tabs, Accordions, Buttons, Alerts, Column grid, Entry likes shortcodes to your theme.
Toolkit Page Builder
The Toolkit handle the page builder admin. The Bon Theme Framework is required to use the page builder.

Bon Toolkit

The Bon Toolkit extends functionality to Bonfirelab's Themes. It provides custom post types build, widgets, and some shortcodes.

Retina for WP vs Bon Toolkit