MK-Cinnamon Roll
Cupcakes (available at all the parks)
France bakery (Epcot)-several items (although they are not open for breakfast)
Norway (Epcot)-school bread (again not open for breakfast, but you could get some on your way out and save for the next morning)
MK (Main Street Bakery): Another vote for the cinnamon roll
Epcot (Sunshine Seasons): Some pretty good muffins
AK (Kusafari): Some breakfast pastries, but the best items (the cupcakes) aren't available until after 11 am.
You might also try your resorts food area...some have some pretty good items.
HS - Starring Rolls (seriously, cherry pastries the size of your head!)
Epcot - France, Norway bakery (after 11 though...) Sunshine Seasons before that
AK - Pizzafari has breakfast selections on snack credits