Responsive Web Design Sketch SheetsThis tool is useful in mapping out the placements of various elements in your website layout across various devices. With the help of this device, you can form an idea of where to place the necessary elements of a website for different screen sizes and resolutions.
Responsive WireframesResponsive Wireframes is an experimental tool created by James Mellers of Adobe. It is built with only HTML and CSS (no images or JS were used) which you can use to visualize how your responsive design would look like on actual browsers of various desktops and mobile devices.
StyleTiles Responsive Design ToolsStyle Tiles gives you a way to develop an idea of how a website would look like, independent of the complicated styles that come into play. It gives you the opportunity for a perfect responsive design workflow and also the ability to integrate client feedbacks.