jQuery is a Javascript library that takes this motto to heart: Writing Javascript code should be fun. jQuery acheives this goal by taking common, repetitive, tasks, stripping out all the unnecessary markup, and leaving them short, smart and understandable
Raphaël is a small JavaScript library that should simplify your work with vector graphics on the web. In case you want to create your own specific chart or image crop-n-rotate widget, you can simply achieve it with this library.
Sarissa is a cross-browser ECMAScript library for client side XML manipulation, including loading XML from URLs or strings, performing XSLT transformations, XPath queries and more.