I finally got around to making my own laundry soap a few weeks ago. I found a "recipe" for it here. The only change I made to mine was instead of theFels Naptha Soap I used Dr Bonners Citrus Organic Bar Soap. This was only because I couldn't find the Fels Naptha at my grocery store and I was to lazy to make a special trip to get it.
So far the laundry soap has been working beautifully. My clothes come out clean and smelling fresh, but not too much like citrus. It's also so much cheaper than store bough detergents. I think when I figured the numbers out its somewhere around .05 cents a load! Also, I only need 1 table spoon of it to do one load of laundry.