I put vinegar instead of fabric softener in my washing machine rinse aid dispenser.
Shannon lush also suggests putting bicarb soda in with the wash section, and using about 1/4 or less the recommended amount of washing powder. I've got a front loader so I think I'd put the bicarb directly in with the clothes than let it get washed in from the powder dispenser. Somebody who has the other books (speed cleaning?) can tell us the right amounts.
She also mentions using a few drops of lavendar oil in a 1 litre of water in a squirty bottle for freshing rooms and getting rid of doggy odours.