We just found a great buffet on Highway 192 at Holiday Trail near Old Town. It's Sizzlin Grill and it's right at the corner of the intersection. $10.99 for adults and I don't really know what for kids (didn't have any). It's billed as a steak and seafood buffet but they have so much more than that. Cheeseburgers, spaghetti and meatballs, grilled chicken, fried chicken, real mashed potato and gravy (smooth and creamy), clam chowder (pretty tasty), chicken noodle soup, five different flavors of jello (including blueberry), strawberry cobbler, ice cream with different toppings, huge salad bar. That's what we had. I didn't even see the steak and they brought out turkey and cranberry sauce since it was Thanksgiving. Drinks are extra but refills are plenty. You can find a 10% discount coupon in the many coupon books laying around.
Another favorite on Highway 192 way down around marker 15 is Shell's, a seafood place. There's also a Joe's Crab Shack near Celebration. And of course, the New York Pizza World next to the IHOP on the west side of World Drive.