I recently came across a cool little application by the name of Singular. The point of Singular is to examine a directory (and sub-directories) for duplicate files. You get the option to find duplicate files by filename, size, or MD5 hash – which is the most reliable in just about every case. Singular will also ensure that one copy of each duplicate file it returns is preserved, so no worry about accidentally deleting something permanently.
The place where I’ve found this app to be most effective is in helping to weed-out my old back-up drives. Back before I established a half way decent process for backing up my computers, it was all over the board, and I know that files were at least in triplicate in some places on my backup drives. So having the ability to drop a folder into Singular and quickly evaluate those duplicate files to clear up unnecessarily used space is great.
If you’ve got ugly backups or are just looking for some extra space on your drives, Singular is a nice tool to have.