Here's a link to the menus (with prices):
http://allears.net/dlr/din/menu/menus.htm
I've found the best values to be:
Pizza Port (in Tomorrowland): The pasta portions are HUGE (enough to split between 2 adults); the pieces of pizza here huge until recently, but they're still fairly large sized. One order of pasta + a piece of pizza = a meal for 2 hungry adults. Free refills on sodas, too.
Carnation Cafe' (on Main Street): Yes, it's a full service restaurant. However, the food is delicious, the portions are huge, and the price is about what you'd pay at the counter service restaurants at the Park. In other words...it feels like a "splurge", but you'd be spending the same to eat hamburgers & fries somewhere else.
Rancho del Zocalo (in Frontierland): ENORMOUS portions. One combo platter can easily be split by 2 adults. Plus, free refills on sodas
For breakfast, Riverbelle Terrace (in New Orleans Square)...their breakfast platters are fairly large & include eggs, potatoes, bacon or sausage, a biscuit or pancakes, and cost around $9. One of the best deals for breakfast in the Park, IMO.
In DTD, Jazz Kitchen Express (the "takeout" section of Ralph Brennan's) has a shrimp, bbq pork, chicken, or turkey po boy sandwich platter that's served with yummy spicy fries. The portion is not just huge, but ENORMOUS! Two adults can definitely split the meal and maybe even have leftovers. Cost of the meal is around $9. Sodas are refillable here, as well.