I watched my first videos on "Rocket Stoves", which can be made from a few $1.70 cinder blocks and one H-block.
Here is the 2 burner model.
These have an elbow which forms a chimney, and the air is "jetted" through due to the hot air rising and "sucking" in more oxygen rich air.
https://www.youtube.com/watch?v=kmDYUrVHPWc
With just a little bit of fuel, you have a very efficient and hot stove.
My Ammo Can Rocket Stove
http://www.freerepublic.com/focus/chat/2914240/posts
Weekly Preppers Ping
Here are some pictures of my completed Ammo Can Rocket Stove.
http://www.freerepublic.com/focus/f-bloggers/2863465/posts
Excellent! I have one made from an old propane cylinder but his is so easy.
ping to my 137
AWESOME!!!!!!!!!!!!!