Tools for Web Designers and Developers
Vanilla5 & Vanilla5 for Wordpress
If you need to start working on creative first there are a couple PSD files based on the 960 grid. It really is the easiest way to get started on your web projects.
A tool to help with math regarding responsive designs. Based on Adobe Air it will work on Windows or Mac OSX. Do conversions into percentages and em's.
Trying to figure out where you break your media queries can be a pain especially if something isn't working correctly. This plugin helps you by displaying the current viewport width as well as what common device is within that range.