I don't make them as often these days, but I still go through spells where I make them daily. I'm in the pro-fat camp, so I tend to include whole-milk yogurt, coconut milk, or peanut butter. I like most eligible fruit but prefer berries most of the time. Mint can be an interesting touch, as can Thai basil.
I've never made any of the green smoothies, but I've enjoyed some of the ones I've tried.