Fat free Greek yogurt!
Yogurt is an all around good food. Even some lactose intolerant folks can enjoy yogurt because of the bacteria cultures present. Now, now, don't worry it's friendly bacteria, and you probably have more bacteria on your keyboard than in the yogurt.
Greek yogurt is even better because of it's reduced milk serum content. It's strained, so it's thick and creamy. It makes an excellent marinade for meat (tandoori chicken anyone?) and a good swap for sour cream. I've also used it to thicken smoothies (not my favorite use, but good one) and I add flavor to plain yogurt all the time to make banana splits. It's also a great low-calorie protein, nonfat varieties tend to have 8-11 grams of protein per 1/2 cup - 3/4 cup serving.
A good on the go snack is an individual sized Greek nonfat yogurt, Fage, Chobani, Oikos and Trader Joe's all make them, and I add a packet (usually tablespoon sized) honey to it. Very tasty and you're reaping the digestive benefits of both the honey and the yogurt!
Dannon also makes a Greek Yogurt, pre-sweetened. It comes in a large tub and 6oz size. Also tasty. I dig the vanilla. You could also make a suitable yogurt cheese by straining your favorite plain yogurt overnight in the fridge with a cheese cloth or coffee filter. Get thee to the Greek.