Take the oEmbed functionality of WordPress and make it automatically responsive. It uses the Iframely API so there is support for literally hundreds of link types, including YouTube, Vimeo, TED, and more.
Embed a variety of filetypes (PDF, DOC, CSV, etc.) right in the browser using the Google Viewer API. Embed documents with a shortcode or an extra button in the WYSIWYG Editor.
Easily create polls on your WordPress posts and pages, and put them anywhere with a shortcode. The plugin can be as robust as you need it to be, and provides plenty of options for expanding the functionality and customizing your polls.
Add Google Maps to your pages with a shortcode or template tag. Has several customizable parameters, and supports the latest static maps API with directions, multiple maps, different map types and KML imports.
Integrate your comments from the Disqus comments service into WordPress. You can moderate and control comments from your Disqus account, and automatically sync, import or export comments that already exist in WordPress. The plugin will store your comments in your database automatically.
Use Facebook comments on your WordPress install. Settings are available to customize the way the comments look and add them to any post or page automatically or with a shortcode.
View your page at different screen sizes right within your browser window automatically. Just chose the size you want to test your site at, or see them all at once, using a drop-down menu in your admin bar.
Add a Google Map to WordPress using this widget. Maps are added as a linkable thumbnail which opens a map in a mobile-friendly Lightbox, so it is perfectly lightweight and customizable.
Use a drag and drop interface to create and edit newsletters, either automatically recurring or one at a time. Pull in content from your WordPress install and customize the look and feel of your newsletter. Mobile friendly.
Create forms with a drag and drop interface, and then add them to your WordPress site with a shortcode or template tag. Several different field types are available, all completely customizable, with add-ons for extra functionality.
Add Testimonials to your site using a custom post type with specific custom fields. Testimonials can be added to WordPress using a shortcode, a built-in widget or template tags.