When you design web sites in the browser you're left alone in the dark without any of your familiar design tools. By nature there's no application you can load up and start building your design. Well, this isn't that. However I think it's the next best thing.
Instead of starting from square one every time you begin a project I think we need a collection of good starting values in markup and css to start designing, and a library of javascript tools to help us rapidly prototype as we think creatively. In the Kit you'll find HTML inspired by HTML5 Boilerplate, a system for writing highly flexible and powerful css with Sass, Compass, Susy, and other frameworks, and a bevy of javascript libraries at your disposal.
The Coding Designer's Survival Kit is two related projects. First is the project on Github, which is not Drupal, but a generalized set of tools for doing this work in any CMS (or none). Second is the theme based on that project, which will have a full release here on drupal.org shortly.