Things I've carried through airport security in the last few months:
Whole/sliced fresh fruit (can't do fruit cocktail or canned fruit)
baked goods of various sorts - rolls, croissant, doughnuts, muffins
crackers, pretzels, chips
sandwiches (but if you do pb&j put it together, they won't let it in seperately)
raisins
dried pineapple
trail mix
granola bars
cheerios (got milk as my 'drink' on the plane)
cheese (hard kind, not creamed)
lunchables packages with crackers, lunchmeat, and cheese in them
The earlier posters were right, in that you can bring a cooler (so long as it is smaller than the standard carryon dimensions) but you cannot bring either ice or frozen gel-type things.
No thermoses or anything like that either.
The airlines will still give everyone a soda/juice/coffee and some who claim that 'all snacks are for sale' still give snack mix. On a long flight, don't be afraid to ask the stewardess 'could i have the can?' during beverage service, they'll give you the whole thing instead of pouring a third of it into a cup for you.
