According to the article at Wikipedia , "Adipocere or grave wax or mortuary wax is the water-insoluble material consiting mostly of saturated fatty acids. It is formed by the slow hydrolysis of fats in decomposing material such as a human cadaver by action of anaerobic bacteria. The transformation of fats into adipocere occurs best in the absence of oxygen in cold and humid environment, such as in wet ground or mud at the bottom of a lake or a sealed cask, and it can occur with both embalmed and untreated bodies. Corpes of infants and overweight persons are particularly prone to adipocere transformation. Adipocere formation begins within a month of death, and in the absence of air it can persist for centuries. An exposed, infested body or a body in warm envirominment is unlikely to form deposits of adipocere. The process of adipocere formation is also known as saponification.
In essence, in this process the usual dissolution of putrefaction is replaced by a permanent firm cast of fatty tissues and even internal organs and face. This allows some estimation of body shape and facial features, and injuries are often well-preserved."
So, basically, in certain environments, the fat in your body can turn into soap - sometimes well preserved enough to be a "soap mummy". Sweet! I always wanted to be creamated, but somehow being a soap mummy sounds way cooler. You need to be somewhere cold, wet, and generally free of insects for it to work best though.
Now, on to
This is the "Soap Woman", a soap mummy on display at the Mutter Museum. She died in the 19th century of Yellow Fever, and the conditions of the soil were such that she basically turned into soap.
There is also a "Soap Man" at the Smithsonian -
I don't know his exact story though.
There used to be some great sites on Adipocere, but sadly the best one seems to be gone :(