I fancy myself the smoothie king-- always trying to come up with something different and wonderful.
My most basic smoothie probably isn't too far off the beaten path of normal experience for people here:
1 banana
Large handful of frozen strawberries
Small handful of frozen blueberries
Two tablespoons of vanilla lowfat yogurt
Healthy dash of grapefruit juice
Dash of pomegranate/blueberry juice
And when I've really earned it-- a scoop or two of Endurox
Now to make it interesting...
Taper back on some of the strawberries and blueberries and substitute a half a can of peaches, mango or apricots (apricots provide a delectable richness). On hotter days, I'll opt for the refreshing properties of a small can of pineapple instead.
I've added peanut butter to my smoothies-- surprisingly good. And whenever possible, I'll take what's left in my coffee pot (usually a quarter to a half a cup), and add that.
A tablespoon of instant coco can be nice depending on what else is going on in the blender.
Until recently, I was fond of (only occasionally) adding a bit of rum to my smoothies, but I've become so much more committed to this hobby as a sport that I've stricken alcohol from my life altogether. Still though-- a post-ride endorphin buzz can be seriously enhanced by a good rum smoothie!