This Is Responsive : Tips, Resources and Patterns for Responsive Web Design
Email Standards Project : The Email Standards Project is about working with email client developers and the design community to improve web standards support and accessibility ...
Email-Blueprints : Email Blueprints is a collection of HTML email templates that can serve as a solid foundation and starting point for the design of emails.
Ink : A Responsive Email Framework from ZURB. Quickly create responsive HTML emails that work on any device & client. Even Outlook.
BackstopJS : Breaking CSS is easy. Checking every responsive page element is hard. That’s why there's BackstopJS.
A collection of patterns and modules for responsive designs.
