What is it exactly? How do I get it? How is it used?
Caffenol is a home-made developer that seems to be gaining popularity among enthuisiasts, especially due to non-toxic compounds and environmentally friendly footprint.
According to Caffenol @Wikipedia:
There are many formulas for caffenol. All are based on preparations which contain caffeic acid (i.e. coffee or tea) and a pH modifier, most often sodium carbonate.
I use 10 teaspoons of Folgers Instant Coffee Crystals, 7 teaspoons of Arm & Hammer Washing Soda, and 1 teaspoon of Ascorbic Acid Vitamin C for the developer. I use a bit of Heinz Distilled White Vinegar mixed with tap water for a stop bath, and 8 oz tap water, 2 oz of Ilford Rapid Fixer for the fixer.
Note that development times are usually longer that off the shelf developers.