This is a member of the Araceae or Aroid family, which are distinguished by having a central spathe surrounded by a single large leaf. They have extremely unusual forms, and often smell of carrion, since they are pollinated by flies.
I am no expert on this genera, but comparing pictures leads me to believe this is Amorphophallus mossambicensis. The Pacific Bulb Society has more information about these unusual plants here http://www.pacificbulbsociety.org/pbswiki/index.php/Amorphophallus, as does the International Aroid Society http://www.aroid.org/aroid/