This past October, I made homemade liquid laundry detergent. I made a half-batch and being I only wash 3-4 loads a week, it has lasted me a while. I figured it cost me a penny a load. So far, it is working nicely. Here is the site that I got the know how from.
Update: the link I had here is not good anymore, so I found a new place to go to with many different recipes. I usually go by # 2, but I only do a fourth at a time being I don't nned as much.
Home made laundry detergent recipes