When I first became interested in saving money I stumbled upon how to make foaming hand soap. I tried it, and it didn't work. Then sometime last year I tried again, and it worked! And my husband actually approved! This is huge because he's very particular about certain things.
Here is how I make foaming hand soap.
What you need:
a foaming soap dispenser
liquid Castile soap
I reuse a foaming dispenser. I use Lavender Glownaturals Essentials Liquid Castile Soap from Vitacost. It's cheaper than Dr. Bronners, and I feel it's very comparable. (if you use my referral link here you get $10 off your first order, and I get $10 too.)
My dispenser has a little bit of foaming soap left in it so let's pretend you're starting with an empty dispenser.
Fill it with about 10mm (1cm or a dime) of liquid Castile soap.
Then add water leaving enough room for the lid thingy to fit inside the bottle. My son likes to shake it up. Then it's ready to use!
I've heard people use leftover shampoo in a pinch.
Soap + water + foaming dispenser = foaming soap!
If I had to guess I'd say that one refill lasts about a week in my house. I have one in the main bathroom and one in the kitchen.