1) Moo.fx - A superlightweight, ultratiny, megasmall javascript effects library, written with prototype.js. It’s easy to use, fast, cross-browser, standards compliant, provides controls to modify Height, Width, and Opacity with builtin checks that won’t let a user break the effect with multiple crazy clicks. It’s also optimized to make you write the lesser code possible.
2) Rico - An open source JavaScript library for creating rich internet applications. Provides full Ajax support, drag and drop management, and a cinematic effects library.
3) Swat - Developed by silverorange, Swat is an open source web application toolkit built with PHP.
4) ColorCombos - Who would’ve thought a color library would end up mixed in with a bunch of JavaScript and PHP libraries? Well they do have a pretty sweet little color library for finding color combinations, all you do is select the color and they show you some nice combos that work with that color.
5) script.aculo.us - Provides you with easy-to-use, compatible and, ultimately, totally cool JavaScript libraries to make your web sites and web applications fly, Web 2.0 style. I’m sure I’m not alone when I say this library is my favorite.
6) Mochikit - A kick-ass lightweight JavaScript library that will help you get shit done fast.
7) Dynamic Drive CSS Library - Here you’ll find original, practical CSS codes and examples such as CSS menus to give your site a visual boast.
8) PEAR - A framework and distribution system for reusable PHP components. PEAR provides the above mentioned PHP components in the form of so called “Packages”.
9) DHTML Goodies - A good sized library of DHTML and AJAX scripts.
10) dojo - Open source JavaScript toolkit that makes professional web development better, easier, and faster.
11) Cross Browser | Toys - Huge JavaScript library.
12) Yahoo UI Library - The Yahoo! User Interface (YUI) Library is a set of utilities and controls, written in JavaScript, for building richly interactive web applications using techniques such as DOM scripting, DHTML and AJAX. The YUI Library also includes several core CSS resources.
