SlabText.js
SlabText is a jQuery plugin that splits headlines into rows before resizing each row to fill the available horizontal space. Basically, it means that your headline will always look great whatever of the client screen size.
Download: http://www.frequency-decoder.com/2012/01/08/slabtext-a-jquery-plugin…
jQuery Masonry
Masonry is a dynamic grid layout plugin for jQuery. Think of it as the flip-side of CSS floats. Whereas floating arranges elements horizontally then vertically, Masonry arranges elements vertically, positioning each element in the next open spot in the grid.
Download: http://masonry.desandro.com/
TinyNav.js
TinyNav.js is a super useful jQuery plugin which allows you to automatically turn a navigation menu into a select for small devices such as iPhones. A must have!
Download: http://tinynav.viljamis.com/
FitText.js
FitText is a simple jQuery plugin that automatically make a text fit the width of its parent element. Perfect for awesome, responsive headlines!
Download: http://fittextjs.com/
Breakpoints.js
Simply define breakpoints for your responsive design, and Breakpoints.js will fire custom events when the browser enters and/or exits that breakpoint. Very useful on complicated layouts!
Download: http://xoxco.com/projects/code/breakpoints/
ResponsiveSlides.js
Slideshows are very popular among the web. Though, forcing them to fit any screen size can be a little tricky. ResponsiveSlides.js allow you to create responsive slideshows, which will look great whatever on any device.
Download: http://responsive-slides.viljamis.com/
Flare
Flare is another jQuery plugin for building responsive and full width slideshows. It is not free but it is absolutely worth $10 as it is very easy to use and visually pleasant.
Download: http://is.gd/flarecwc
FitVids.js
A lightweight, easy-to-use jQuery plugin for fluid width video embeds. It was built by was built by Chris Coyier and Paravel.
Download: http://fitvidsjs.com/
Responsive tables
Does your tables break your responsive layout? If yes, here is a simple JS/CSS combo that will let your tables adapt to small device screens without everything going to hell. A must have for any tables!
Download: http://www.zurb.com/playground/responsive-tables
jq-idealforms
Ideal Forms is the ultimate framework for building and validating responsive HTML5 forms. It is super easy to use.
Download: http://elclanrs.github.com/jq-idealforms/