I'm on Day 5, my first Master-Cleanse too. I'm a major foodie and the hardest part so far has just been thinking about food for a couple hours a day, although I've only had legitimate hunger pangs twice.
These are things that I found helped:
You're right, yoga is great.
A hot bath really mellows out my mind and cravings and soothes my tummy if its overworking.
I talked on the phone ALOT today, it's nice to catch up and I think I've got a good friend and my sister interested in doing the cleanse.
A nice, easy walk.