sample app:

<ul>
 <li><img/></li>
</ul>
<script type="text/javascript" src="http://yui.yahooapis.com/3.0.0/build/yui/yui-min.js"></script>
<script type="text/javascript" src="http://github.com/davglass/yui-yql/raw/master/yql-min.js"></script>
<script>
//ref: http://davglass.github.com/yui-yql/
YUI().use('yql', 'node', function(Y) {
 var q1 = new Y.yql('select source from flickr.photos.sizes where photo_id in (select id from flickr.photos.search where text="panda" and safe_search="true")');
 q1.on('query', function(r) {
     var li = Y.get('li');
     for (var i = 0; i < r.results.size.length; i++) {
         if (-1 !== r.results.size[i].source.indexOf('_s')) {
             var clone = li.cloneNode(true);
             clone.query('img').set('src', r.results.size[i].source);
             Y.get('ul').append(clone);
         }
     }

 });

});
</script>

Update 12/13/10 YUI 3 now supports YQL natively: http://developer.yahoo.com/yui/3/yql/