Edit in JSFiddle

// 'node' and 'yql' are both YUI3 core modules that are available for import.

YUI().use('node', 'yql', function(Y) {
  
  // Specify the YQL query
  var query = 'use "http://derek.github.com/sandbox/hackallstars/mediasearch.xml" as mediasearch; SELECT * FROM mediasearch WHERE query="puppies";';
  
  // Define the response handler that is executed when YQL responds with data
  var responseHandler = function(response) {
    var count, html = [], items, item;
    
    items = response.query.results.item;
    count = items.length;
    
    // Loop through each media item
    for (var i = 0; i < count; i++) {

      // Snag the item from the array
      item = items[i];

      // Create the HTML for each item
      html.push("<div class='item'>");
      html.push(" <div>" + item.source + ": " + item.title + "</div>");
      html.push(" <img src='" + item.thumb + "'>");
      html.push(" <hr />");
      html.push("</div>");
      
    };

    // Smoosh the HTML together
    html = html.join('');
    
    // Insert it into the #tweets node
    Y.one("#items").set("innerHTML", html);
  }
  
  // Execute the query and send the result to the callback function
  new Y.YQL(query, responseHandler);

});

<!-- Hacked together by Derek Gathright (@derek) -->

<div id="items"></div>