I know that it sounds weird, but I put ricotta cheese in my smoothie this morning. I was out of milk and wanted to add something to make it more substantial. I figured I'd give the ricotta a try. It gets very smooth in the blender, and adds a little sweetness.
1 medium, very ripe, banana
1 c. chopped pineapple
1/2 c. blueberries
1/4 c. part-skim ricotta cheese
2 c. ice
1/2 c. cold water
Place all ingredients in blender. Blend on medium speed for 2-4 minutes until smooth. Enjoy!