Soapnuts are the dried nuts from the soapberry tree, and you use them as a detergent, in place of regular washing powder. We tried them for the first time today, and they work really well – you simply put a few nuts in a little fabric bag and put in with the wash. As a natural detergent they don’t cause allergenic reactions, and the waste water from washing has minimal environmental impact. This also means that dealing with the resultant greywater will be easier.
It seems that you can use them to wash most things, but we’ve started with clothes, and will have a go at boiling some up to make a liquid soap to use around the place.
We got ours from  who have a great website explaining everything you could possibly need to know about soapnuts..