Don't re-invent the wheel. Here are some places where you can find scripts and libraries and other code snippets:

Client Side Script Libraries

• JQuery.com -- Javascript library
• Script.aculo.us -- web 2.0 Javascript
• DynamicDrive.com - DHTML scripts
• YUI -- Yahoo User Interface library
• Prototype Javascript Framework
• Dojo - Javascript toolkit
• Dijit
• Google Web Toolkit
• ExtJs.com

Other Libraries

• RegexLib.com - Regular expressions library

Useful Scripts

• Coda-Slider -multiple panels that you can navigate via tab or left/right arrows