I don't know if this one has been posted before, but this was on one of the news programs the other day.I haven't got a chance to try it yet, but it looks pretty easy.
1 cup baking soda
1 and 1/2 cups washing soda
1 and 1/2 cups borax
1/2 cup liquid soap- Ivory
2 cups white vinegar
Start with liquid soap, add in dry ingredients.
Add small amounts of vinegar and stir until all has been added.The mixture will change from a frothy foam to a powder.
Stir on and off for about 1/2 an hour , until it is more powderlike than foam
Store in a sealed container, use 1/2 cup for lg. load.