Awesome
CasperJS responsive size screenshots
Simple script to help you out when working with responsive views.
Just call casperjs responsive-screenshot.js --url=URL from terminal/prompt, where URL is the URL you want to screenshot.
The script will save to responsive-screenshots/DATE/SLUG-WIDTH-HEIGHT.png
Example:
casperjs responsive-screenshots.js --url=http://twitter.github.com/bootstrap/examples/fluid.html