I fight that same urge to snack at night. I've made some progress by:
1. Never have potato chips or icecream in the house. If I know its there, it calls my name.
2. Keep a calorie log. (i'm using fitnessjournal.org but im sure there are others) Just by having to write down what i am eating, and how many calories, i dont let myself go out of control with the munchies.
3. Keep Kashi granola bars, sugar-free popsicles, sugar free jello, Dannon LightNFit with fiber yogurt stocked in the house. These items have easily countable calories on the package. I just let myself one "unit". (if i had a bag of chips or cookies...like the ad used to say "noone can eat just one."

Its good to know I'm not the only one struggling with these issues.