Fleegix.js: Simple. Useful. JavaScript.

Fleegix.js provides an extremely lightweight, cross-browser set of JavaScript tools for building dynamic Web-app UIs.
Fleegix.js includes the basics of what you need to build an Ajaxy Web app:
A concise but powerful events system
An industrial-strength XHR library
JSON and Web form serialization
CSS manipulation
Visual effects
To keep the toolkit small, more specialized features are broken off into optional plugins, including:
JavaScript Dates with Olson timezone support
a simple, no-muss-no-fuss XML parser
a sortable Hash
useful date utilities such as strftime, add, and diff
Some color conversion utilities
Most of the plugins can be used standalone with your JS toolkit of choice.
Fleegix.js does not attempt to coerce JavaScript into behaving like Python, Ruby, Java, or any other language -- the code is plain, ordinary, idiomatic JavaScript. Simple, but potent stuff.
It is well tested in the major-market-share browsers -- Firefox 1+, Internet Explorer 6+, and Safari 2.
Fleegix.js is licensed under the Apache License, Version 2.