I dont really believe in any of them... she died from an overdose of barbiturates. I dont believe the one that says JFK had her killed because JFK had many girlfriends which are still alive. However some of the evidence ive heard are interesting.... so who knows.
ps. have you heard the rumore that she had six toes? snopes kills that..
http://www.snopes.com/movies/actors/mmtoes.htm