2 cups frozen fruit
1 cup fresh fruit
1/2-1 cup juice (depending on how thick you want it)
1/4 cup yogurt (plain, vanilla, flavored, whatever)
As much fresh or frozen spinach as you can get away with (I usually do about 1/8 cup)
1. Blend until smooth. Vary as desired.
Notes: I'm pregnant and I live in the desert, these are pretty much a staple at my house. I find them to be a good way to use over-ripe fruits. Last night's smoothies were a mixture of papaya, mango, cantaloupe, pineapple, blackberry, honey dew, banana, spinach, strawberry and lime. (I read once that papayas are good for indigestion.) I also threw in about 1/4 cup of prepared strawberry jello because we had it in the fridge and it is an easy-to-digest source of added protein. I have found that if you use fruits like mango or papaya, you need to add a little bit of citrus for best flavor. So if you're using one of these and don't have any citrus handy, just add a teaspoon of lemon juice. I have also used canned pineapple in place of the fresh fruit and the juice.
To cut down on the cost of fruit I freeze my own. If I have a bunch of fruit that's going to turn before we eat it, I chop and freeze it. A couple of months ago Bountiful Baskets was offering a case of 9 pineapples for $14. I bought one and chopped and froze half of them. I've done the same with cases of mangoes, peaches and blackberries.