Using jQuery from Google CDN doesn't work
In Drupal 6, you cannot use drupal_add_js to add external JS files. You need to use drupal_set_html_head. Thankfully, in D7 this has been fixed.

drupal_set_html_head('&lt;script type="javascript" src="https://www.google.com/jsapi?key=my site"&gt;&lt;/script&gt;');
drupal_add_js('google.load("jquery", "1.6.4"); google.load("jqueryui", "1.8.16");', 'inline');