extjs 3.3: floating panel
var testPanel = new Ext.Panel({
                                id: 'testP',
                                width: 50,
                                height: 100,
                                floating: true,
                                title:'Test'
                            });
testPanel.show();

Ext.Panel({

  //.. other config..,
  floating : {
    //Ext.Layer config options. Maybe a property in that will get you the desired effect that you're looking for.
  }
});