WP-Migrate allows users to enter database information separate from the current site/blog database, and migrate the current information over. It enables you to select what (if any) information to move over, and/or update the URL throughout the database to a new domain while keeping the serialized meta information intact.

Responsive Page Tester:  When viewing the front end of the site, a "Responsive" button is added to the WordPress Toolbar. Clicking that will toggle an overlay with your website presented in various sizes for easy responsive design testing. This can be useful both during theme development, and when writing content to verify it will be presented properly.