Video: Take a Tour of the Body Farm
VBS.TV has a three part documentary about the Body Farm field laboratory in Knoxville, TN.
A body farm is a research facility where human decomposition after death can be scientifically studied in a variety of settings. The body farm in Knoxville has been in operation since 1981 and over 700 bodies have entered the facility (Wikipedia entry).
The creator of the body farm, William Bass, wrote a book back in 2004 which I've read and is very interesting (if you're into that kind of thing).