Duplicate Files Finder is a cross-platform application for finding and removing duplicate files by deleting, creating hardlinks or creating symbolic links. A special algorithm minimizes the amount of data read from disk, so the program is very fast.
This program does not let you work on a per folder basis. Let's say there are two folders, A and B. Let's say there are 80% duplicates between them and you have about 1000 files in each. You can't tell the program to delete all duplicates from folder B for example. You have to do each file individually (not feasible for me).