Get all Folders in a library using SPServices.

var LibName="";
var folders = "";
function GetLibraryFolders()
{ jQuery().SPServices({
operation:  "GetListItems",
listName: LibName,
asunc:false,
completefunc: function (xData, Status) {
    jQuery(xData.responseXML).SPFilterNode("z:row").each(function() {
      var thisFSObjType = jQuery(this).attr("ows_FSObjType").split(";#")[1];
      if(thisFSObjType == 1)
folders  = folders+  jQuery(this).attr("ows_LinkFilename")+"\n";
    });
}
});
alert(folders  );
}