This is the original XML implementation of the hack. This is just for reference and will not be updated

Code:
<!-- Begin AJAX Categories -->
<script type='text/javascript'>
//<![CDATA[
var gCat;
function getCat(cat) {
   var url= '/feeds/posts/summary/-/' + cat + '?max-results=5';
   var pars = '';
   gCat = cat;
   
   var myAjax = new Ajax.Request(
       url,
       {
          method: 'get',
          parameters: pars,
          onComplete: showCat,
          onFailure: showFail
       });
   showLoading('search-result');
}
function showCat(output){
   var main = output.responseText;
   main = main.replace('<img ','<img style=\"display:none\" ');
   out = parseXMLFromString(main);
   var xentry=out.getElementsByTagName("entry");
   var xtitle, xcat, xcontent;
   $('search-result').innerHTML="";
   
   var meta = document.createElement('div');
   meta.className="search-result-meta";
   var link=document.createElement('a');
   link.href="/feeds/posts/summary/-/"+gCat;
   link.innerHTML = "<img src=\"http://i15.photobucket.com/albums/a355/deepakr/feed-icon.gif\" title=\"Subscribe to this category\" /> Subscribe To " + gCat;
   meta.appendChild(link);
   $('search-result').appendChild(meta);

   for (var i=0;i<xentry.length;i++) {
      xcat=xentry[i].getElementsByTagName("category");
      xtitle = "";
      xcontent = "";
      catdisplay = "<div class=\"search-cat\"><span style=\"color:silver;\"> Sorted into:<\/span> ";
      for (var j=0;j<xcat.length;j++) {
         catdisplay = catdisplay + xcat[j].attributes[1].nodeValue;
     if(j<xcat.length-1)
         catdisplay = catdisplay + " , ";
      }
      xtitle=xentry[i].getElementsByTagName("title")[0].childNodes[0].nodeValue;    
      xcontent=xentry[i].getElementsByTagName("summary")[0].childNodes[0].nodeValue;
      xlink=xentry[i].getElementsByTagName("link")[0].attributes[2].nodeValue;
      if (xtitle != "") {
         $('search-result').innerHTML = $('search-result').innerHTML + "<h3 class=\"search-title\"><a href=" + xlink + ">" + xtitle + "<\/a><\/h3";
         $('search-result').innerHTML = $('search-result').innerHTML +  xcontent + "...";
         $('search-result').innerHTML = $('search-result').innerHTML + catdisplay + "<\/div>";
      }
   }
   $('search-result').innerHTML = $('search-result').innerHTML + "<div class=\"search-close\" onclick=\"javascript:new Effect.Fade('search-result')\">Click to close<\/div>";
   $('search-result').style.display="block";
   new Effect.Highlight('search-result');
}
function showLoading(id) {
    $(id).style.display="block";
    $(id).innerHTML="<img src=\"http://i15.photobucket.com/albums/a355/deepakr/loading.gif\"><i>Loading...</i>";
}
function showFail(){
   $('search-result').innerHTML="Sorry! The page cannot be loaded.";
   $('search-result').style.display="block"
}
function hideCat() {
    $('search-result').innerHTML="";
    $('search-result').style.display="none";
}
function parseXMLFromString(text)
{
  // code for IE
  if (window.ActiveXObject)
  {
    var doc=new ActiveXObject("Microsoft.XMLDOM");
    doc.async="false";
    doc.loadXML(text);
  }
  // code for Mozilla, Firefox, Opera, etc.
  else
  {
    var parser=new DOMParser();
    var doc=parser.parseFromString(text,"text/xml");
  }

  // documentElement always represents the root node
  var out=doc.documentElement;
  return out;
}
//]]>
</script>
<!-- End AJAX Categories -->