Well, unfortunately the "negative calories" thing is untrue; all foods have only positive calories, and none of them cost more calories to digest than they contain. Still, when you're talking about single-digit calories as in celery and cucumbers, it's such a small number that a lot of people do consider them freebies.
I only count mine to keep track of nutrition; I certainly don't worry about the calories they contain. I assiduously weigh out my breakfast cereal and other carbs, weigh or measure calorie-dense fats, and portion out avocados and such on the scale, but I don't keep careful track of my green leafy vegetables. I tend to estimate those because treating them as a "go ahead, pile it on" kind of food encourages better eating habits in myself.
Others' mileage may vary, of course.
And I would love to play D&D if I had more people in my neighborhood who played--but I used to play like a fiend. Fatferretfanatic is another 3FC gamer chick, so we're not too scarce around here.
