Finding Duplicate Images

[Mhardy]

First a question, then some background. Is there any software that can find duplicate pictures based on the actual image, not the file size or name?
I'm scanning three households worth of family photos (parents and grandparents). I know there are duplicates in there (I have seen a few). What I do is scan several pictures together as one file to lessen the total number. Once they're home, I separate them in to individual files and sort them. So, the duplicates probably won't have the exact same file size nor the same name. So, I need something if it exists that will LOOK at the content of the picture and say "These look pretty similar" Does anything like that exist?