Survival Soap!

A commonly forgotten item on trips, camping and otherwise, is soap.  However, it is fairly easy to make in the wild.  Items you will need:

Wood ash or charcoal from your campfire
Water
Oil or fat (either animal or vegetable)
For antibacterial purposes you can add pine needles or pine resin, although it is not necessary.  Plus it will give your soap a pleasant smell.
A stick for mixing.  This is important as the wood ash and water mixture is highly alkaline, and can burn your skin
A filter or strainer, a piece of cloth will do

Making the Soap
After the fire has cooled a bit, collect charcoal and/or wood ash from the center.
Grind the charcoal into a fine powder.
Using the stick, stir water into the powder. Mix it well, and then strain it through your filter, reserving the water.
Heat the oil or fat and mix the reserved filtered water into it.  Bring this to a boil.
If you have chosen to use pine needles, grind a handful and add them to the mixture.  Boil until all the water has evaporated.
Take the mixture from the fire and allow it to cool completely.  If you have a small mold (altoids tin?) you can pour it into one.  You now have a basic soap!