I've been making my own laundry detergent for seven years now and occasionally get asked about the recipe so I thought I'd share it here.
It's easy to make, effective, and inexpensive (costing around $.14 a load). With three little boys, I do roughly 5-6 loads of laundry a week. This last batch lasted a solid nine months!
You can find all the ingredients stacked together at Wal-Mart in the laundry aisle, or scattered a little at most Targets (it's hit or miss for me). You can also buy them all together on Amazon for a little more money.
One box of 20 Mule Team Borax 65oz
One box of Arm & Hammer Washing Soda (not baking soda) 55oz
Three bars of soap (not detergent) like Fels-Naptha or Dr. Bronner's
1 tub of Oxi Clean (optional- good on stains, but not "natural")
Roughly chop your bars of soap and put in a food processor until they're crumbled into bits around the size of a pea or smaller.
Combine all ingredients into a 2 gallon canister (something like this) for use. I pour in half the ingredients, mix, pour in the second half, and mix again. It makes a lot!
Use around 1 Tablespoon per load.
I'm usually asked if it really gets out stains and my answer is a resounding YES. If something doesn't come out, I soak in oxiclean and water and then re-launder the next day. I rarely have a problem.