Duplicate Cleaner - Duplicate Cleaner: the fastest and most popular tool for finding duplicate files. Over 1 million downloads: Get your copy now! Free and Pro versions available.
dupeGuru - dupeGuru is a tool for finding duplicate files on your computer.
DupDetector - Dup Detector finds duplicate and near duplicate images by opening and reading image pixel data.
AntiDupl - AntiDupl.NET can find and display duplicate images in the main graphic formats: JPEG, GIF, TIFF...
VisiPics - VisiPics does more than just look for identical files, it goes beyond checksums to look for similar...
rmlint - A commandline tool to find unnecessary files (duplicates, tmpfiles, unstripped binaries and more)