How to make homemade laundry detergent for US $1.88 for an 8 month supply (10 gallons).
1/2 cup washing soda
1 bar solid laundry soap (Fels-Naptha or similar)
Grate laundry soap bar on cheese grater. Place in saucepan with 2 cups of water or so, and heat on medium heat while stirring until all the chunks are melted. Pour this into a 5 gallon bucket. Add washing soda and borax. Add more boiling or REALLY hot water to bucket to fill it to the top, and mix it all well. Cover with plastic wrap or a lid and let sit overnight (or at least 15-20 hours). The next day, it will be all congealed. Mix this up well with a large wooden spoon or your hands, and divide the mix equally between two 5 gallon buckets. Fill both buckets to the top with more boiling/really hot water. You now have 10 gallons of detergent. Using a ladle and a funnel, pour this into smaller containers (such as old juice jugs, milk containers or similar), and store. Use as needed. This 10 gallon batch lasts about 8 months, so I cut it in 1/2 and make 5 gallons total, and its a little easier to manage storage-wise