Having a huge playroom and napping rooms means I can deduct a large portion of our housing costs. I find saving money there to be the most noticeable. We've got to live somewhere and it's great to save a chunk (living in Calgary which is quite expensive if you want a large yard etc).
The biggest saving to me is being with my kids - a savings of stress and emotional energy. While running a Dayhome is not without its stressful moments, most of the stressors can be eliminated by me.
I still love shopping, so I don't save as much on clothing as I should....