I have one in the beginning stages being made out of a 20lb propane bottle. I also plan on making a heater attachment to stand on top of it to capture more heat before it vents out of a shelter or what have you. Sort of like the rocket mass heater thing I linked in that other thread about rocket stoves. Mine will be something like this one:
TIG WELDED Stainless Rocket Stove Home-Camp & Emergency - eBay (item 330431124275 end time Jan-31-11 20:28:08 PST)
but with a few differences.