I have been on a smoothie rampage as of late and have learned a thing or two that I'd like to share!
Smoothie milk base: I always use vanilla soy milk as the base. I honestly don't really care for vanilla soy alone, it's got a weird texture and taste, but it seriously makes the BEST smoothies. Hands down. It adds such a rich and delicious taste. People always comment on how good my smoothies are -- it's the vanilla soy. It's great stuff and it keeps for a long time in the fridge, like a month or two, so buy vanilla soy. I usually start out with about a cup of vanilla soy with each smoothie. If you like thicker smoothies, put less.
Frozen yogurt cubes: I just love the Very Vanilla Lowfat Yoplait Yogurt. Excellent stuff for smoothies. I make frozen cubes of yogurt to add to my smoothies. I fill an ice cube tray up with 2 things of yogurt and freeze them. So one thing of yogurt will make about 8 cubes. Perfect for smoothies. Seriously.
Bananas.... they go in EVERYTHING! For real! We have been going through bananas like crazy! So I buy tons. I usually peel and cut up a whole bunch and then stick them in the freezer for later. If I found that I bought too many bananas and they start to turn pretty brown, I make banana bread :)
Strawberries: I'm cheap. Really. So I don't buy frozen strawberries. I go to Costco and buy a big huge thing of fresh strawberries and then I take them home, pit them, and then stick them in my freezer so they don't go bad.
Oatmeal: Oatmeal is a great and delicious way to add more substance and nutrients to a smoothie. It's was weird the first time I had oatmeal in a smoothie but I love it now and I usually end up putting 1/4-1/2 cup in a smoothie.
Flax: This adds wonderful texture and nutrients to a smoothie. Try it.
Spinach: It's always freaky to see a green smoothie. Or one that just looks like it's been through someone's digestive system. But you honestly can't taste it! Spinach is SOO good for you and you can't taste it so just throw some in!