Here is a description from a site that sells soapnuts (there are many sites that sell soapnuts, this site just happened to have a good description):
Maggie’s Soap Nuts™ are the only laundry soap that grows on trees! Truly effective, 100% natural and safe for your most sensitive skin. Soap Nuts™ are the dried fruit of the Chinese Soapberry tree. They contain saponin, a natural cleaner used for thousands of years to clean clothes, just like the plants used by Native Americans for washing.
Simply put a few Soap Nuts into the included cotton sack and drop it in your laundry. Your clothes come out clean, vibrant, and soft. Replace your laboratory detergents and softeners with the soap made from Nature by Nature. Your clothes, your skin, your family, and your planet will thank you.
I've yet to give them a try, but from all I've read online, they sound like a very healthy, inexpensive alternative to laundry soap. Additionally, you can add your own scent to your wash by using a few drops of pure essential oil.
Several months ago, I combined great sales and coupons to get quite a large amount of laundry soap. I think I still have about 7 or 8 bottles left. Most of it is unscented and dye-free, so I am planning on using the rest of it before I buy my soapnuts. Plus, soapnuts are available on Amazon.com, so I am saving up my Swagbucks money to make my purchase!
Please let me know if you've tried them, and how they work for you!
Image is also from above link.