The JavaScript Framework Matrix, by Mathias Schütz, is a well-presented comparison of the popular JavaScript frameworks.
It shows examples for most of the functions which gives a strong idea on the coding principles of every framework.

The libraries included are:

  • jQuery
  • MooTools
  • The Dojo Toolkit
  • Prototype
  • Script.aculo.us
  • Ext.JS
  • Adobe Spry
  • BBC Glow
  • Yahoo UI! Library
Every function/snippet provided links to the original documentation which is nice for reading more on the resource.