well right now, I'm trying out DeCloner. It does certain things OK but I have noticed that it also has missed some obvious duplicates and triplicate files and frankly, I don't know why.
I was looking at sorting through several different back up drives, and started wondering about what kind of software was available to find duplicates.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic