I was reviewing the Smoothie King, amazed that the sheer majority of them include carb-rich calories, usually 80%!
But there are some stand-outs. At only 187 calories, the very tasty Gladiator has less than 1 carb and packs 45g protein. I recommend blueberries and blackberries as your two fruit blends. Their turbo blenders make it light and delicious.
Also consider the Low Carb Smoothie. Only a bit higher in calories (225) and carbs (6), it packs in 35g of protein. The Chocolate Shredder kicks up the carbs to 42g, but has a respectful 36g protein.
Beware protein and workout sounding smoothies such as Power Punch or High Protein. These are mostly just 400+ carb shakes with barely respectable amounts of protein less than 10g.