1 cup baking soda or washing soda
1 cup borax
1/2 cup salt
1/2 cup citric acid
Use 1 tbs per load. Add vinegar to the rinse aid compartment of your dishwasher to help prevent clouding.
The initial cost of the items might cost more than you would pay for one bottle of dishwashing soap, but you will be able to get more washings out of the total ingredients.
I'd love to hear if you have tried any thing like this before!