You've gotten some great suggestions! I use a blender, and do yogurt + banana + strawberry. You could also use whatever is in season- peaches, blueberries, etc.
I also sometimes put a spoonful of honey and/or a spoonful of brain/wheat germ in it. Smoothies are a good way to "sneak" some of those healthy add-ons in without disrupting the flavor too much.
A handful of spinach, well-blended, is also a great addition. It adds a ton of nutrients and very few calories. It doesn't disrupt the taste very much, but it definitely gives a bright-green color to your drink!