I have two boxes in the laundry/utility room and three boxes in the Florida room. I took an idea from Jazzcat's "litterbox room" and added a cat flap to the laundry room door that leads outside to the Florida room. The boxes themselves are huge Rubbermaid storage containers.

I am thinking about just putting all of the boxes outside since they spend so much time there and this keeps the litter out of the main house. I also do not like to walk barefoot into the laundry room and get litter on my feet!