0 
0 I just googled across this open source project. It is relatively simple, but can be quite useful. Its demos are at any rate useful, if only for the JavaScript they show:
* Autocomplete- Retrieves a list of values that matches the string entered in a text form field as the user types.
* Callout- Displays a callout or popup balloon, anchored to an HTML element with an onclick event.
* Select/dropdown – Based on a selection within a dropdown field, a second select field will be populated.
* Toggle – Switches a hidden form field between true and false and at the same time switches an image between two sources.
* Update Field – Updates one or more form field values based on response to text entered in another field.
The AJAX Tag Library is a set of JSP tags that simplify the use of Asynchronous JavaScript and XML (AJAX) technology in JavaServer Pages.
AJAX is primarily rooted in JavaScript. However, many server-side developers do not have an extensive knowledge of client-side programming in the browser. It’s much easier in some cases for J2EE developers, especially, to simply add a JSP tag to the page to gain the function desired.
This tag library fills that need by not forcing J2EE developers to write the necessary JavaScript to implement an AJAX-capable web form. The tag library provides support for live form updates for the following use cases: autocomplete based on character input to an input field, select box population based on selections made from another field, callout or balloon popups for highlighting content, refreshing form fields, and toggling images and form field states on/off.
The implementation is a combination of Java classes and JavaScript source files. The Java code should be OS independent as there are no client side components. However, the Java is dependent on JDK 1.4+ and requires a Servlet container to run. The JavaScript should run in at least Firefox 1.0+ and Internet Explorer 5.0+.
See: http://ajaxtags.no-ip.info/
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Hi, Lucas! Thanks so much for posting about AjaxTags. As a developer on the project, it’s always good to see kind words about the project. Just to let you know, we’ve released version 1.1-Beta1 just yesterday. Check it out, then hop over to the forums to let us know what you think. http://ajaxtags.sourceforge.net/
Interesting article that dissects the Google Suggest functionality. This is probably where the recent AJAX hype started: http://serversideguy.blogspot.com/2004/12/google-suggest-dissected.html