I LOVE Fiber One, but I usually need to add some banana or berries in to give it some more flavor. I also like Fiber One mixed in yogurt... yum!
Other than that, even though it has more calories, I love granola. I like the Zoe's brand. They have a Honey Almond Granola that is delicious.
If you are into hot cereals, oatmeal (cooked on the stove not the instant) and cream of wheat are great. You can add sugar or sweetener to either one if you want. I like brown sugar and cinnamon in my oatmeal.
Edited to add - Lately for breakfast though I have been having smoothies. 1 c fat free plain yogurt, 1 cup 1% milk, and 1 cup of frozen mixed berries (or other frozen fruit. bananas and grapes work great too!) VERY filling plus I'm getting a lot of my calcium and some of my fruit/veggie servings in there.