I am not the inventor of this stove, and there are far better designs out there (Penny Stove is the best!), but this pressure-based alcohol stove is by far the easiest to make.
Watch the video for an overview:
Step 1: Supplies
1. Two pop cans, or beer cans.
Make sure the bottom of the can is free of dents and scratches.
2. Fine sandpaper.
320 or higher grit.
3. Utility knife blade.
5. Wire hangar.
6. Fiberglass (optional, but recommended).
I used insulation from the basement.
7. Bottle of Heet.
You can also use denatured alcohol, everclear, or 91% isopropyl alcohol.
Step 2: Sand the cans
Make it as smooth as possible to ensure a tight fit and prevent leaks.
You'll need to empty one of the cans, so go ahead and have a drink while you work on the second one. The second one needs to be full and sealed, so don't drink it yet!