Aww shucks, not what I thought this thread was about...moving on...
Is it necessary to have a yogurt base for the smoothie? I have some vanilla ice cream on hand so I can use that with the juice and some frozen berries I have, as well as ice. Does the yogurt make a big difference?
Well, only if you believe that *all* yogurt base are belong to you. 
Who knew a thread about smoothies would be so amusing?
To answer the OP's questions, I started drinking smoothies last spring as part of my weight-loss regimen (I refuse to call it a diet.) I had a bad habit of sticking to the 3 square meal formula and waiting so long in between meals that I was ravenous by the time I ate ... which meant throwing caution to the wind all too often. I try now to eat more smaller meals.
I make a smoothie in the morning and take it on my commute to work. It's a great way to start the ol' system going in the morning, and it keeps me from doing something stupid like stopping at McDonalds or something on the way to work.
I do not use a yogurt base, as I prefer mine more "drinkable" and less like a milkshake. I always add banana to mine, though, which does tend to add a creaminess to them.
I like to mix it up as far as ingredients go, so as to keep it from getting monotonous. I tend to use whatever's in season during the spring and summer, but lean toward strawberries, blueberries, raspberries, etc.; maybe some mango or kiwi if it's available; peaches, nectarines and apricots can be good, too. when that kind of fruit is no longer available, as someone else said, frozen fruit is a great option. There is all kinds available, and it tends to be pretty affordable. With the frozen fruit, I'll throw it in the blender and pour the liquid over (I like pomegranate with a splash of OJ and some fat-free milk) and let it sit while I'm showering and such, which tends to let the fruit thaw just enough to make a nice smooth smoothie when it's blended.
So, that's it for me. hope it helps, and enjoy your smoothieing.
Oh, and one final note: I was given a "Magic Bullet" as a gift a few years ago, and find it works perfectly for making smoothies. It comes with 4 mug containers with handles so your blending vessel acts as your drinking vessel as well. bonus.
