Below is the link to plans for what appears to be the greatest residential slush maker ever.
It is basically a 5 gallon drink dispenser (Like you see on football sidelines, orange gatorade things) with a (new) garbage disposal mounted underneath, add a little PVC plumbing and you have one whopper of a slush maker. Just add the ice, water & drink mix and turn it on. The disposal grinds ice. The neat part is that you can put a recirculation pipe into the system so the ground slush gets recirculated, so you will get a nice, smooth consistancy.
I have never built one myself, but it looks like it would work!