Sugar augments the existing JavaScript environment with helper methods on existing objects. From fixing broken support of standard methods, widening acceptable arguments, multi-lingual and improved regex support on strings, nice supplementary string methods like words(), and shortcut methods to Math object methods. Additional helpers for Dates, Objects, Functions and Regex. An library for a consistentising JavaScript across different imlementations.
Thomas Fuchs offers a JavaScript powered application that allows developers to filter down to find the most appropriate JavaScript micro-library or micro-framework for their project. There has been an explosion of mini-libraries in the JavaScript world as web developers get to grips with more complex and rich user interfaces and web applications.
Christian Heilmann describes an approach to building complex web application by basing them around events, particularly around YUI's CustomEvent class.