1 over-ripe banana (When bananas get too ripe, I peel them, put them in a zip-lock bag and freeze them. When I make a smoothie, I microwave the banana for about 30 seconds before putting it in the blender.)
1 cup yogurt (I usually use vanilla)
about 1/2 cup vanilla soy milk
1 cup frozen berries (We get a large bag of them at Costco.)
Blend till smooth. It's pretty thick depending on how much milk you add.
This makes enough for 2, so if it's just for yourself, you can easly 1/2 the ingredients.