I can't say enough good things about steel cut oats for breakfast. But make sure you have a little protein with them, like skim milk or yogurt on top, or a few nuts; before I figured that out I used to be starving about 3 hours later.
There are other whole grains you can similarly use for breakfast -- barley, or wheat berries. I cook them sometimes when I have run out of the oats. You don't have to eat them sweet either. They take a while to cook, but I cook up a batch (about 1 1/2 cups dry) for a whole week and keep them in the fridge to warm up in the morning. About 1/4 cup makes a full cup cooked, at about 150 cal, with 5 grams of the 25 carb grams being fiber, plus 4g protein.
The dense black European rye breads, that come in rectangular packets, have a similar nutritional profile -- a good amount of fiber and protein going with the carbs. They are almost completely whole rye grains. They are good with strong flavored fillings; I like cream cheese and salmon (also high protein). It's the kind that looks like this:
http://en.wikipedia.org/wiki/Pumpernickel
My German grandmother faithfully ate a piece every morning for her "Darm" (er, digestion to put it politely). It may seem odd at first if you are not of Northern/Eastern European heritage.
Only if you don't have a lot of fiber in your diet now, work up to to the full serving slowly...