I kind of thought "no," but I've brought ice through security a few times this year without problems. Indeed, last weekend, I had a quart sized bag of ice tucked into a bag of food and had no problems even though the TSA went through every item in my luggage for other reasons (see contact lens thread).

Given the absence of food on most domestic flights, I often like to bring some food with me -- especially when I travel with my kids. I feel better about bringing things like cold cut sandwiches if I can keep them somewhat cool.

A couple years ago there was some joking that the TSA was ignoring physics by treating ice as a "liquid," but I don't think there was ever any actual rule issued. Does anybody know if a TSA rule on ice exists?