Ajax接触不久，我只是为了挑选一款 Ajax 库，才收集的资料，并测试，我的测试很简单，直接看他们网站上的联机demo页面的速度，速度慢的就淘汰！

辅助js:
www.formassembly.comwForms 44k（压缩版）
对表单的js扩充可实现本地校验等功能。
Ajax:

http://www.sarmal.com/sardalya/Download.aspx
不错！速度快!有hint控件。75k. free for non-commercial

http://openrico.org
感觉好像不错，也比较小，这个侧重于远程客户端抓取，不过也有控件！而且可以和wForm联动。
不过它的网格控件比较弱，不支持键盘。
License
Rico is provided free and open-source (Apache 2.0 License) for either your personal or commercial use.

http://dojotoolkit.org/
不错，功能挺全的，但是它的核心js文件有128k，然后还要动态装入其它的js, 太大！！速度慢！！
dojo.js 是它的核心(128K)，然后其它widgets是根据需要装载，所以在使用的东西太多的情况下显得慢。
dojo.js:
Dojo's bootstrap system provides some fundamental behaviors, including a package system for dynamically loading scripts.
The Dojo Toolkit is only one of the projects that the Dojo Foundation hosts. In addition to the toolkit, OpenRecord calls the Dojo Foundation home.

http://www.htmli.com
不错，速度快！！不过需要客户端的XSLT的支持！幸好的是IE和FireFox1.5都支持！！
嘿嘿，才发现它的lib.js 居然有189k！但是速度一点不慢！
HTMLi (HTML improved) is the open source framework that focuses in:
    * Transparent use for HTML designers
    * Multi-platform: As it is 100% designed with XSL, it is 0% platform-dependant
    * CSS Themes, Multi-Language support
    * Fully customizable & extensible
    * XML Rich Forms allow simple AJAX interfaces
俺的选择！俺认为使用客户端处理 XSTL 是速度提升的关键，而且这样一来， html代码扩充显得很自然。

http://sharengo.org/jsria/test/allComponents.html
感觉速度还可以！！注意必须要在服务器上运行！！它用了net.XmlHttpRequest
http://sharengo.org/Wiki?JsRIA

JsRia - Javascript Rich Internet Application (since 2005)
[3] JsRIA is a opensource framework enabling rich client interface development. It's pure javascript and is completely independant of the server side technology. The client interface is described by an xml file (or dynamically in javascript if you need that). JsRIA is completely object oriented (javascript components, xml description, css style) and you can very easily build a hierarchy for your interface objects. You also can use AJAX technology to bring really dynamic interface to your users. Numerous functions are provided to parse and use xml flux coming from your server.

http://qooxdoo.org/
速度慢！！但是控件漂亮！！只适合于Intranet,它的js高达几百k(qooxdoo-0.5.2-build.tar.bz2)，不过qooxdoo-0.5.2-source.tar.bz2,中是拆分成若干js的！！
qooxdoo (Under development; from May, 2005)
qooxdoo is an advanced open-source JavaScript-based GUI framework. It helps you to implement AJAX-enhanced web 2.0 applications - easier than ever before.

    * Open-source (LGPL). From various contributors.

http://script.aculo.us/
Script.aculo.us (from 2005)
Scriptaculous builds on Prototype library to provide a Javascript with comprehensive Ajax coverage.
    * Visual Effects (See One-Second Spotlight pattern)
    * Drag-And-Drop (See Drag-And-Drop pattern)
    * Unit-Testing (See System Test pattern)
    * etc.
    * Open-source by Thomas Fuchs and others. A project run in conjunction with Ruby on Rails, but can be (and certainly is) used independent of Ruby or RoR.

Google Web Toolkit
Google Web Toolkit (GWT) 是一个Java软件开发框架用于开发类似于Google Maps和Gmail 的AJAX应用程序. 你可以用Java编程语言开发你的界面,然后用GWT编译器将Java类转换成适合浏览器执行的JavaScript与HTML.
主页 http://code.google.com/webtoolkit/