It's amazing how much hard drive space can be taken-up by duplicated files.
Decloner helps you recover lost disk space and eliminate duplicate files on your Mac. The developers guarantee a high degree of accuracy due to the use of an SHA-1 algorithm to determine if files are identical. Using Decloner is easy. Simply browse to the file or directory that you want to scan for duplicates and click Scan. Depending on the size of the folder, scanning can take a while but Decloner is very accurate at identifying which files are possible duplicates.
You can choose whether to keep the oldest or newest or Trash items manually. The good thing is that whatever you do, nothing is really lost. All removed files are moved to the Trash can so you can restore them if the worst happens. You can use QuickLook to examine the contents of suspected duplicate files or folders just as you would in Finder. Note that Decloner also works for external drives as well.
It's a little slow at scanning and it would have been nice if it supported dragging and dropping of files but overall, Decloner should save you at least some disk space.