When a question is closed as a duplicate, links to the "proposed duplicate" questions are added to it.
I'd like to see a sort of index, or table of these duplicates. For each proposed duplicate question on SO, I'd like to see the list of links to the questions of which it's a duplicate.
This might help in locating frequent duplicates; in choosing the oldest good duplicate question; and possibly in creating FAQ pages on the subjects most frequently duplicated.