J Query.black and White
Clientside grayscale images on any browser
Color
JavaScript color conversion and manipulation library
Js Barcode
Barcode generation library that works in both the browser and on Node.js http://lindell.me/JsBarcode
Im.js
Image Match - Project to allow compare different images pixel by pixel with good performance
Rimg
A responsive image solution for browsers that support mediaqueries. Pure javascript and no server-side code.
Drawingboard.js
A canvas based drawing app that you can integrate easily on your website.
Breathing Halftone
Images go whoa with lots of floaty dots
Mapmap.js
A data-driven API for interactive thematic maps
Soc.js
An easier way to create social icons
Gif.js
JavaScript GIF encoding library
Img to Ascii
A JavaScript implementation of a image to Ascii code
Focal Point
A small set of CSS classnames to help keep images cropped on the focal point for responsive designs. Using only HTML/CSS, web authors can specify an image's focal point, which stays as the image's primary focus, while the image's available width changes on responsive webpages. Crop and re-size images depending on available width and let CSS to do all of the work, and without any JavaScript.
Obelisk.js
JavaScript Engine for Building Isometric Pixel Element with HTML5 Canvas
jQuery QR Code
qrcode generation standalone (doesn't depend on external services)
Paper.js
The Swiss Army Knife of Vector Graphics Scripting – Scriptographer ported to JavaScript and the browser, using HTML5 Canvas. Created by @juerglehni & @jonathanpuckey
Easel JS
The Easel Javascript library provides a full, hierarchical display list, a core interaction model, and helper classes to make working with the HTML5 Canvas element much easier.
Html2canvas
Screenshots with JavaScript