AllDup
http://www.alldup.info/download.htm#alldup

Anti-Twin
http://www.rosenthal-software.com/en/antitwin/
http://www.joerg-rosenthal.com/en/antitwin/download.html

Auslogics Duplicate File Finder
http://www.auslogics.com/en/software/duplicate-file-finder/

CloneSpy
http://www.clonespy.com/?Download

Double Killer by Big Bang Enterprises
http://www.bigbangenterprises.de/en/doublekiller/download.htm

Duplicate Cleaner Free
http://www.digitalvolcano.co.uk/content/duplicate-cleaner
http://www.softpedia.com/get/System/File-Management/Duplicate-cleaner.shtml

Duplifinder
http://duplifinder.codeplex.com/

Easy Duplicate Finder
http://www.easyduplicatefinder.com/

Exact Duplicate Finder
http://indeepsoft.blogspot.co.uk/2012/10/exact-duplicate-finder.html

SearchMyFiles by NirSoft
http://www.nirsoft.net/utils/search_my_files.html

WinMerge
http://winmerge.org/index.php