The bakery in France has the aforementioned ham-and-cheese croissants, and also bacon rolls, which are snack credits good for breakfast (if you can stay away from all of the other stuff, that is...)
I like the smoothies at Auntie Gravity's in Tomorrowland at MK too - strawberry, tropical, orange-pineapple, or coffee flavored, made with nonfat yogurt too. A nice, portable snack-credit breakfast item.
We also enjoy hitting the "produce" spots in each park for breakfast-y snacks, too... grapes, pineapple, yogurt, apples-with-caramel, etc., kind of a build-your-own version of the yogurt parfaits mentioned by a prior poster.