This is a short example on how to use javascript to get an auto complete text field. It works in all modern browsers. It is similar to the one used by Google suggest.
Developer: vonloesch.de Platform: linux, windows, osx Date upd:2005-04-22 Hits2342 [Visit]

This useful script allows you to target a form's submission to a new customizable window, so the original page does not change once the "submit" button is pressed. Instead, a customizable pop up window is launched containing the destination page.
Developer: javascriptkit.com Platform: Date upd:2003-05-27 Hits4196 [Visit]

This script validates a date field to ensure it's in the format mm/dd/yyyy. It also intelligently checks that the date ranges are valid, so something like 02/30/2005 is caught.
Developer: JavaScript Kit Platform: linux, windows Date upd:2005-11-01 Hits2087 [Visit]

wForms is a javascript extension that adds commonly needed behaviors to traditional web forms. It follows the principle of progressive enhancement : unobtrusive, cross-browser and degradable. I should also point out that not a single line of code is required to actually use it.
Developer: Cédric Savarese Platform: linux, windows, freebsd, osx, sun Date upd:2005-08-29 Hits4409 [Download] [Visit]

Validator widgets work on your form input fields to validate common types of data like e-mail, urls, ip addresses, phone numbers etc. Part of the jaxWidgets component library.
Developer: Sarat Pediredla Platform: linux, windows, freebsd, osx, sun Date upd:2005-06-27 Hits2216 [Visit]