Nice Friend turned me onto this recipe to make your own laundry soap. I don't know if it really uses less packaging than buying regular laundry soap, but it's certainly cheaper. I spent just a little over seven bucks, and I probably have enough detergent to last for a year. After using it for a few weeks, I feel comfortable saying it works well--especially on whites. Plus it smells good, and the little pink shreds of grated soap are way fun!
The recipe (originally from Tipnut, which has lots of other recipes too):