I plan for snacks...but for me, they are mini meals and must include some protien. If I don't plan them, I tend to pick at the stuff that has little nutritional value and then find myself hungry all day anyway (and eating more).

typical snacks:
yogurt w/ protien powder and granola
rolled up lunch meat eaten with fresh fruit of some sort
light cheddar cheese with an apple
cold chicken and fresh fruit
1/2 a protien bar
carrot sticks, raw green beans and a small handful of almonds
1/2 a protien smoothie
ff ricotta with apple butter and chopped walnuts
powerbutter on wheat crackers