I found an "IQ Puzzle" at http://www.robmathiowetz.com, and, being bored and a geek wrote up a solution:
Let D,F,M,P,S,T represent the Daughter, Father, Mother, Policeman, Son, and Thief (respectively). Then the initial state is:
I worked out a solution (as follows). I haven't had a chance to write up a state-space search version to see if there are any shallower solutions, but its still pretty fun. My wife and I really enjoyed this one.