How do you find who has the most mutual friends with you on Facebook?

http://www.facebook.com/apps/application.php?id=5685209393

that works. however, i think they only search through YOUR friends. so if the person who you have the most mutual friends with is not your friend on fb, they won't come up.

However, there is a very good likelihood that the non-friend with the most mutual friends will be listed on the "People You May Know" page, so the above tool (which may not be currently active as of February 2012) combined with the "People You May Know" page provides a fairly definitive answer.