I thought this website was taking the piss, but it actually seems to work.
You input a photo and it uses some advanced facial recognition software to find your best match. I thought I'd trick it by uploading a few photos of actual Hollywood Celebs and it matched them up with the actual people. Wierd.
I actually don't look like anyone. The best it came up with was a 54% match with Kevin Costner... Does anyone remember Water World?
Sally had an 86% match with some chicks called Amanda Bynes and scarily enough, they look kinda similar.
Enjoy!
http://www.myheritage.com/