Thanks for all the tips, everyone!
I now have a direction to go in. I need to figure out where I can get lye locally. I'm okay with using lye, I'll be careful!
Here's the laundry soap recipe I use:
Three ingredients (four if you have hard water, or if you want it scented; five if you have hard water AND want it scented):
Soap of some sort (recommended is Fels Naptha or Ivory bar soap, but others can be substituted; Fels Naptha is usually in the laundry aisle)
Washing Soda (to remove dirt and odors; not the same thing a baking soda; washing soda will be in the laundry aisle)
Borax (to whiten and deodorize; 20 Mule Team is the brand I use, also in the laundry aisle)
Water softener, if you need it (White King water softener is the powder I use)
Essential oil (for scenting the laundry soap; I've also used scented soap instead of unscented soap and skipped the essential oil)
Ingredient proportions:
1/3 bar Fels Naptha or other type of soap, as listed above
1/2 cup washing soda
1/2 cup borax powder
1/2 cup water softener powder
up to one ounce of essential oil
Grate up your bar soap and melt it in a pot in 6 cups of water.
When the soap is completely melted add the powdered ingredients and stir until they are completely dissolved.
Remove from heat.
In a 2+ gallon bucket add 4 cups of hot water, then add the soap mixture, stirring well.
Now add 1 gallon plus six cups of water and stir.
Store in the plastic bucket with plastic wrap over the top, or use a funnel and pour it into empty laundry soap containers.
It must sit for 24 hours to gel to the appropriate consistency (which will still be more watery than what you're used to; it will resemble egg drop soup or chicken noodle soup).
I use 1/2 cup for medium/regular loads, up to a full cup for super-size loads (I have a super capacity plus washer) or really dirty work clothes of Mark's.
Some tips I've read online suggest doubling the washing soda and/or borax if it isn't getting your clothes as clean as you'd like; also doubling just the soap ingredient if you want the finished product to be thicker and more gelled.
I always use a whisk to stir the finished product once in awhile as it's gelling, to break up any clumps of soap that might try forming.
The first time I made this I didn't let the soap and powders dissolve and melt together, so it was way more chunky than I like. The second time I made sure to heat it all long enough and used a wire whisk that it blended together well.
No matter what, I think it will always appear not quite mixed and not quite gelled, but it works really, really well, and is SUPER cheap. It breaks down to less than a penny per load, if you can find the ingredients for cheap. I think I paid about $2 for the bar soap, about $7 for the borax and about $5 for the washing soda. I've made three batches of soap so far and have over 3/4 of the borax and washing soda left.
I got this from the site tammysrecipes.com , but the basic recipe is floating around numerous other sites, too.
I really like it!