md5-imgs is a little script I did to find duplicates in my directories.

Use the script is really simple, just drop a line like:
  $ md5-imgs.rb <directory to check>

By default the script doesn't write anything to the disk, if you want to delete duplicates you have to set 
DELETE_DUPLICATES variable to 'true'.

The script calculates md5 of files and uses them to check duplicates. It's really (really really) difficult a false 
positive but it's still possible.