Just thought I'd share my new favorite trail food. Stroopwaffles. These are huge in Europe, but only starting to pick up in the US. Stinger makes a version called Stinger Waffles which are basically the same thing.
They are super flat, east to pack, hold up well (don't smash too easy), and pack 160 calories per ounce!
If you sit them on top of a mug filled with coffee, they get all warm and gooey. And since they are so sweet, I pair them with black coffee and no longer need to carry sugar or Splenda.