I've been making my own cleaning products for some time now and love the way that so many different types of cleaners can be made from 6 basic ingredients: baking soda, washing soda, borax,
castile soap, vinegar, and lemon juice. I make glass cleaner, an all purpose spray cleaner, soap for the wood floors, scrub for the bath tub, soap for the dishwasher, and even shampoo out of these ingredients.
Recently I decided to test out some homemade laundry soap. I've been using Charlie's Soap, which I completely love, but I can no longer get locally, so I decided to look to my current products for an answer. I was already using washing soda and/or Borax in addition to my regular laundry soap sometimes when I needed a laundry booster or something for odors or tough stains. And my Dr.
Bronners castile soap touts that it can be used to clean just about anything. So why not mix them up?

I ended up grating an ounce of the Dr.
Bronner's, then adding a cup of Borax and a cup of Washing Soda. I shook it all together and stored it in a glass jar w/ tight fitting lid. I use about 2 tablespoons for each load (just because that's how big the scoop is in my laundry room).

Our laundry comes out looking, feeling and smelling nice and clean. No fake "mountain fresh" or "sunshine" scent, just clean. There's no plastic waste. Everything comes in cardboard, which I recycle. And it's all stuff that I buy anyway. Gotta love that!
EDITED 2/27/09 to say: As you'll see in the comments below, we were asked for a cost per load on this laundry soap. We originally figured it at a much higher price (because I'm not all that good at math, evidently!). I looked online for prices of the Washing Soda and Borax because I didn't remember how much I'd paid for them 6+ months prior. Well, when I went to our local King Soopers grocery store (owned by Kroger) to restock this week, I found that they were
much cheaper than I found them online. So here is my new cost breakdown:
COSTS:
Washing Soda: 3.99 for 55 oz = .072 / oz
Borax: 3.49 for 76 oz = .045 / oz
Dr. Bronner's bar: 3.65 for 5 oz = .73 / oz
For one batch I use:
8 oz Washing soda = .576
8 oz Borax = .36
1 oz Dr. Bronners = .73
for a total cost of = 1.66 per batch
One batch = 17 oz of mixed product
2 tbsp = 1 oz, so there are 34 tbsp of product in this batch
$1.66 divided by 34 tbsp = .048 per tbsp
I use 2 tbsp per load, so that is $0.097 (let's round up to $.10) per load
Hope that helps!