[jQuery] from builtwith.com, with love: jquery leads ahead
i know... but still not bad at all:
MooTools
MooTools is a compact, modular, Object-Oriented JavaScript framework
designed for the intermediate to advanced JavaScript developer. It
allows you to write powerful, flexible, and cross-browser code with
its elegant, well documented, and coherent API.
0.78% of all profiled sites use MooTools.
JQuery
Query is a fast, concise, JavaScript Library that simplifies how you
traverse HTML documents, handle events, perform animations, and add
Ajax interactions to your web pages. jQuery is designed to change the
way that you write JavaScript.
2.33% of all profiled sites use JQuery.