Here is a Homemade Laundry Soap recipe, courtesy of Ace Hardware:

1 box of super washing soda 3lb 7oz
1 box of Borax 4 lb 12oz
1 box of pure baking soda 4lb
3 bars of Fels-Naptha soap 5.5oz
(optional) 1 container of Oxy-Clean 1.3lb

Grate the Fels-Naptha bars using a cheese grater or food processor into a fine consistency. Pour each of the ingredients into a large container and mix well. (Use 1-2 tablespoons per load. It can be used in high-efficiency washing machines.)