I use frozen strawberries, bananas and peaches and a small amount of apple juice. Using frozen fruit, especially the banana, gives your smoothie the perfect consistency - no ice needed.
My little sister has a personal favourite... vanilla natural yoghurt, scrape a vanilla pod in there, tbsp of honey, tsp of vanilla extract, pour in a little milk. It's VERY vanilla but that's what she likes, and it IS actually pretty good and healthy. You can make it with fruit flavoured yoghurt and throw a little of the fruit in there too.