Ruby script to remove duplicated files, I created it when migrating my pictures collection from iPhoto to picasa, and merged some independent collections, it created a real mess, and the result of this big mess is this gist.

remove_dups.rb

require 'digest/sha1'
require 'fileutils'
directories = [
  "SOURCE DIR 1",
  "SOURCE DIR 2"
]
files = {}
directories.each do |dir_name|
  puts "Scanning Directory: #{dir_name} "
  Dir.glob("#{dir_name}/**/*.*") do |file_name|
    unless File.directory?(file_name)
      print "."
      dig = Digest::SHA1.hexdigest(File.open(file_name,'rb'){|f| f.read })
      arr = files[dig] || []
      arr << file_name
      files[dig] = arr
    end
  end
  puts ""
end
total_files = files.inject(0){|acum,val| acum + val[1].size}
with_copies = files.select{|k,v| v.length > 1 }
puts "#{files.size} different files"
puts "#{with_copies.size} files with copies"
puts "#{total_files = files.size} duplicates"
FileUtils.mkdir_p "CopiesTrash"
with_copies.each do |k,v|
  orig = v.pop
  puts "moving #{v.length} copie(s) of #{orig} to CopiesTrash"
  FileUtils.mv v, "CopiesTrash", :force => true
  puts ""
end
puts "Your directories are cleaned up of duplicated files, all the trash is in the CopiesTrash folder"

I think the right code in line 25 might be: puts "#{total_files - files.size} duplicates"
Very usefull code. It helped me a lot. Thank's