If you have photos on your Mac, there are almost certainly duplicates. Maybe you copied a folder when you meant to move it, or imported twice without realizing it, or even made some minor edits but kept the original around. Regardless, these extra shots take up valuable space on your hard drive. Gwinno Software’s PhotoSweeper ($10) exists to clean up those duplicates. Instead of working with just one app, it’s a solution for iPhoto, Aperture, and Lightroom, plus any random folders you have lying around.
PhotoSweeper uses a hash-based examination of your photos, eliminating the possibility that you are deleting files based on the same name, similar images, or other factors. It allows you to automatically view photos from the supported apps, and drag in folders containing photos. It’s a very accurate and reasonably fast way of cleaning up your library.