One part Dawn dishwashing liquid mixed with two parts HYDROGEN PEROXIDE. Add baking soda for scrubbing help. Use laundry brush to work into the stain. Supposed to actually take yellow armpit stains out of white shirts!
This didn't seem to do anything for the dishwasher, but I did find a lot and clean out a lot of soap buildup. DIY Dishwasher Tune up. Don't buy a new dishwasher! Four easy steps that will get your dishwasher really cleaning again.