I made this wee beauty from an old paint tin, a tin of dried baby milk and a tin of pineapple chunks. Additional equipment: a hammer, nail, old scissors, tin-opener and pliers.
The principle of the TLUD is simple - burn the gas, not the wood. As wood is heated it gives off various gases in a process known as pyrolysis. Usually these rapidly combine with oxygen resulting in a relatively inefficient local burn, but if you heat the wood in the relative absence of oxygen, the gases can be channelled for secondary combustion. The result is a very clean, efficient burn that delivers most of the wood's energy to the gas flame. If used for cooking, it is many times more efficient than an open fire. You need a lot less fuel, and you generate a lot less smoke. The applications for the developing world are obvious. Since it generates charcoal, you can bury this as biochar, making the process carbon negative - ie you are effectively removing carbon from the atmosphere.
So spread the TLUD gospel! Get out and make your own! Experiment with different designs and tweaks.