Selectize is the hybrid of a textbox and <select> box. It's jQuery based and it has autocomplete and native-feeling keyboard navigation; useful for tagging, contact lists, etc.
common, streamable interface for synchronizing data
autoNumeric is a jQuery plugin that automatically formats currency (money) and numbers as you type on form inputs. It supports most International numeric formats and currency signs including those used in Europe, North and South America, Asia and India (lakhs**).
jQuery Shuffle Plugin
localStorage wrapper for all browsers without using cookies or flash. Uses localStorage, globalStorage, and userData behavior under the hood
A jQuery typing animation script.
2D physics engine for games
A cross browser rich text editor with an API
Can do JS, better, faster, easier.
Beautiful math in all browsers