jQuery: http://jquery.com/
UPDATE: All of the files that I edited for this session can be downloaded here:
http://emma.openflows.com/~nat/jquery/jquerygarland.tar.gz
What you will need to play along with the modules I am using, and the files that I am modifying
Drupal 6.4
CCK:
http://drupal.org/project/cck
http://ftp.drupal.org/files/projects/cck-6.x-2.0-rc7.tar.gz
Imagefield:
http://drupal.org/project/imagefield
http://ftp.drupal.org/files/projects/imagefield-6.x-3.0-alpha2.tar.gz
FileField:
http://drupal.org/project/filefield
http://ftp.drupal.org/files/projects/filefield-6.x-3.0-alpha4.tar.gz
ImageAPI:
http://drupal.org/project/imageapi
http://ftp.drupal.org/files/projects/imageapi-6.x-1.0-alpha2.tar.gz
JSTools:
http://drupal.org/project/jstools
http://ftp.drupal.org/files/projects/jstools-6.x-1.0.tar.gz
Lightbox2:
http://drupal.org/project/lightbox2
http://ftp.drupal.org/files/projects/lightbox2-6.x-1.8.tar.gz
jQuery UI Tabs
http://drupal.org/project/tabs
http://ftp.drupal.org/files/projects/tabs-6.x-1.0.tar.gz
CCK Fieldgroup Tabs
http://drupal.org/project/cck_fieldgroup_tabs
http://ftp.drupal.org/files/projects/cck_fieldgroup_tabs-6.x-1.x-dev.tar.gz
Active menus
http://drupal.org/project/activemenu
http://ftp.drupal.org/files/projects/activemenu-6.x-1.x-dev.tar.gz
jQuery Cycle Plugin
http://malsup.com/jquery/cycle/download.html
Additional notes
For users using Drupal 5.x, if you want to use many of the newer jQuery plugins, you must use the jQuery update module found here:
http://drupal.org/project/jquery_update
This requires replacing the jquery.js, and associated js files distributed with Drupal core. Depending on how you perform security upgrades, you may need to do this every time you move up a point version.
There are many other modules that use jQuery and interact with Drupal but I have never tried them, and cannot vouch for their quality. There are also a ton of jQuery plugins out there.
JQuery and AJAX
The JCarousel module is here
http://drupal.org/project/jcarousel
I don't think it implements AJAX itself, but the JCarousel JQuery plugin the module uses does:
http://sorgalla.com/projects/jcarousel/examples/dynamic_ajax.html
A little more on AJAX from Victor Kane's Drupal plus JQuery session at DrupalCampLA at about the same time we were in New York.