Content of HTML table cells can be dragged to another cell or another table. It isn't difficult to define onMouseMove handler and change top / left element styles to move the object. In case with tables, you will have to determine somehow destination cell. Attaching onMouseOver handler on TD elements will not work, because browser doesn't fire events to the elements beneath the dragged object.

School timetable is example of how to use REDIPS.drag library. Page layout contains two tables: left table with school subjects and timetable on the right. After subject is placed to the timetable, button in the same color will be displayed next to the subject (clone object).