I just found MMM this summer, so this is easy enough. I was spending $600 on groceries for two people, but now it's half that. What was I buying? I can't even remember. Must've been a lot of processed food, plus a lot of waste. We also used to drive to the store, but now we walk. I'm ashamed to say how close it is to us. We ate out a lot too, usually multiple times a week, just because it was easier and we were being lazy. Now we're badass and don't rely on that as a crutch, so eating out is a special event. I lost ten pounds, too. We've also cut our electricity expenses dramatically, though I'm convinced we could do more there.
I'm looking forward to following this thread to see what people who are more optimized than me are cutting.