Resizer, a handy new tool for testing out your responsive UI.

http://design.google.com/resizer/

Weld - from idea to prototype, in minute

https://www.weld.io/

Froont - Design Responsive Websites With Ease

http://froont.com/froont/start-vers-2

Statti - Responsive Bootstrap Animated Template

http://themeforest.net/item/statti-responsive-bootstrap-animated-template/5033222

Responsive Email Patterns - A collection of patterns & modules for responsive emails

http://responsiveemailpatterns.com/

Responsive Strategy

http://bradfrostweb.com/blog/post/responsive-strategy/

Meet Gridset - create complex grids in an easy-to-use interface

https://gridsetapp.com/features/

The Pros and Cons of Responsive Web Design vs. Native App vs. Mobile Website

Native vs. Mobile

12 Premium Responsive Landing Page Templates

http://mashable.com/2014/02/05/responsive-landing-page-templates

Interactive website demonstrates the difference between fixed, fluid & responsive layout

http://liquidapsive.com/

Webflow - Design Responsive Websites Visually

http://www.webflow.com/

FROONT - Responsive web design, the visual way

http://froont.com/

Weflow - Design Responsive Websites Visually

http://webflow.com/

Responsive Prototyping with UXPin

http://uxpin.com/

Responsive Navigation Patterns

http://bradfrostweb.com/blog/web/responsive-nav-patterns/

Adaptive Vs. Responsive Layouts

                  http://uxdesign.smashingmagazine.com/2012/11/08/ux-design-qa-with-christian-holst/

Divshot - Risponsive Interface Builder

http://divshot.com/

Combining Responsive and Adaptive Strategies to Solve Mobile Design Challenges

http://uxmag.com/articles/combining-responsive-and-adaptive-strategies-to-solve-mobile-design-challenges

Infographic: Responsive Web Design

http://thedeependdesign.com/infographic-responsive-web-design/

‘This Is Responsive’: Everything You Ever Wanted to Know About Responsive Design

http://www.webmonkey.com/2012/09/this-is-responsive-everything-you-ever-wanted-to-know-about-responsive-design/