This takes a little advance prep, but well worth it.
Peel a few bananas, put them in a ziplock bag and store in the freezer until they are hard frozen. A few hours should be enough, but I just keep some in the freezer all the time. They'll keep for months.
When you're ready for a frozen treat, place 1 frozen banana in a blender or food processor with 1 tablespoon of milk or yogurt, and a drop of vanilla extract, then processes until smooth and creamy. Add more milk if needed. The texture should be like soft-serve ice cream.
Enjoy!
Tips:
Ripe, brown-spotted bananas give the strongest banana flavor, and solid yellow bananas give almost no banana flavor so you can really adjust it to suit your taste.
For variety, use different flavors of extract (almond, orange, root beer, etc) or add other frozen fruit (raspberries, peaches, blueberries, etc).
P1 Banana Icecream yummy
Start May 2011: 
