Twitter's Bootstrap with themes, apps, and other enhancements
A lightweight, pure JavaScript library for responding to CSS media queries.
Tips, Resources and Patterns for Responsive Web Design
StyleDocco generates documentation and style guide documents from your stylesheets.
Animate.css is a bunch of cool, fun, and cross-browser animations for you to use in your projects.
Principles of writing consistent, idiomatic CSS
Sprite Cow helps you get the background-position, width and height of sprites within a spritesheet as a nice bit of copyable css.
An easy to use, powerful, and flexible framework for building prototypes and production code on any kind of device.
Font Awesome, the iconic font designed for use with Twitter Bootstrap. In a single collection, Font Awesome is a pictographic language of web-related actions.
With SpritePad you can create your CSS sprites within seconds. Simply drag & drop your images and have them immediately available as one PNG sprite + CSS code. No fiddling in Photoshop, no manual assignment of CSS styles.
Build responsive, mobile-first projects on the web with the world's most popular front-end component library.
Bootstrap is an open source toolkit for developing with HTML, CSS, and JS. Quickly prototype your ideas or build your entire app with our Sass variables and mixins, responsive grid system, extensive prebuilt components, and powerful plugins built on jQuery.
A flexible guide to developing sites small and large.
Teach your forms some manners!
A modern, HTML5-ready alternative to CSS resets
Normalize.css makes browsers render all elements more consistently and in line with modern standards. It precisely targets only the styles that need normalizing.
Online code editor and playground.
CSS Lint points out problems with your CSS code. It does basic syntax checking as well as applying a set of rules to the code that look for problematic patterns or signs of inefficiency. The rules are all pluggable, so you can easily write your own or omit ones you don't want.
Email Blueprints is a collection of HTML email templates that can serve as a solid foundation and starting point for the design of emails.
This website and its sample code creates a template of sorts, absent of design or layout, that will help you avoid some of the major rendering problems with the most common email clients out there — Gmail, Outlook, Yahoo Mail, etc. While not plug and play (you know, you'll have to do some work ;-), it will provide some helpful examples and snippets that will keep your email design rendering as true-to-form as possible.
‘320 and Up’ is a lightweight, easy to use and content first responsive web design boilerplate.