ColdFusion.Tree.getTreeObject gets the underlying YAHOO.widget.TreeView object for the specified HTML format CFTree control. I have used this to create a function that changes the selected tree node, and dynamically opens/closes tree branches based on a user interacting with other elements of the page.
ColdFusion.Window.getWindowObject gets the underlying Ext.BasicDialog object for the specified HTML format CFWindow control. I haven't used CFWindow much yet, but I was just reading through the documentation and the "addButton" function caught my eye. It creates a Ext.Button object that looks much like a form button element, and you can create event listener to react to the button being clicked. This could be useful in a lot of situations.