PortalMods.com

AutoCompleter - using jQuery(Ajax), PHP and MySQL, Tutorial and demo included.
http://nodstrum.com/2007/09/19/autocompleter/

An ajax file manager/file browser which may be used stand-alone, or as a plugin.
http://kfm.verens.com/

Here’s another AJAX login form example using php, javascript and css.
http://joeabiraad.com/ajax/ajax-login-form-php-javascript/89

Nice and simple to use code snippet to use ajax for validating unique user names.
http://www.mellowmorning.com/2007/10/05/ajax-for-unique-usernames/

TohDoh is another cakephp ajax todo list demo.Plenty of interactive features.
http://www.devmoz.com/blog/2007/04/14/introducing-tohdoh-yet-another-cakephp-ajax-todo-list-demo/

PHP and JS File Manager featuring an EXT JS based drag/drop interface.
http://extplorer.sourceforge.net/