The following demo is based on that found at #5 in Mozilla's Debug | XBL menu, i.e. here.
It uses XBL to create a widget that functions as a board for PostIt notes. We create a widget for the board. Its child divs are the notes. In this example, we create a -moz-binding that enables the user to define a board and to supply notes that can be dragged around on the board.
I added code to dynamically create notes and delete them on the fly. The E button edits the contents of the note, and the X button deletes it.