I try to hit up the healthier spots, here's what I've found;
MK: Harbor house (QS), or Liberty Tree (TS)
EPCOT: Sunshine Seasons (QS), Tangierine Cafe (QS), if you like sushi and/or tempura, the various restaurants at Japan are nice
AK: Satu'li all the way (my favorite QS in all of WDW)
DHS: Good luck (lol), but I would look at the various menus online and the offerings at Anaheim Produce and that area, for example Rosie's All-American Cafe has a fried green tomato sandwich.
For breakfast, often I get a side order of eggs, and that's it. Or, eggs and fruit.