Bookmarklet by Benjamin Keen which automates an idea by Lennart Schoors where the current page is loaded into a bunch of differently sized iframes, so when working on a large monitor, you can see what a design looks like at a bunch of different smaller sizes quickly and all at once.
Responsive Design Testing Bookmarklet
DigitalOcean provides cloud products for every stage of your journey. Get started with $200 in free credit!