I have a great app on Windows system called Supercat. You can create catalogs of files based on various criteria, then you can search catalogs for duplicate files also by many different criteria. You'll get a list of only the duplicate files and you can choose to delete the ones you don't want.

I would love to have an equivalent program for the Mac. Anybody know of one? It must do what I outlined above; although there are many file management programs out there I haven't been able to find one that does exactly what Supercat does.