DupeCheck is a little droplet that helps you find and remove duplicate files. What is a droplet you might ask? It's a mini application that acts when you drop a file onto it. Droplets are generally limited to one action, like finding duplicates with DupeCheck.
After downloading and unzipping DupeCheck, place it somewhere where you'll be able to drag files onto it easily. The developer suggests your desktop, but I'd put it in the Documents folder instead. You'll see that as soon as you drop a file onto it a new window opens up to show you all the possible matches. However DupeCheck will only indicate the path to duplicates for you. You'll then have to erase files yourself.
I did find DupeCheck a little slow in searching for duplicates, although the fact that the application is tiny and very easy to use can make it a handy addition to your set of programs.