MK -
Columbia Harbor House without a doubt. That hummus sandwich is just delicious. The big surprise for me was the bread. The bread quality is AMAZING. Good hearty delicious sandwich bread. Nice chewy crust, soft middle. Just perfect. My husband thought I was crazy when I insisted we eat there, but he is now a convert. He had the tuna sandwich and was SO pleasantly surprised. They also have a vegetarian chili which is very well-reviewed, but I have not yet had the pleasure of trying it.
AK - We didn't find anything very good. Pizzafari seems to be the only option. I am intrigued by the picnic in the park option. Haven't seen a review of the actual veg sandwich though. If you're just in the mood for a snack, we had some onion rings at Flame Tree and they were good.
Epcot - There are two REALLY good options:
Sunshine Seasons in Future World (Land Pavilion) is a food court with lots of options. I had the asian selection which gives you 4 asian sides: garlic udon Noodles, stir fry vegetables, white rice, and broccoli. This was infinitely better than it sounds. They also have a soup and salad station, as well as a vegetarian sandwich. Tons of choices for everyone - carnivorous friends as well.
The other option is
Tangierine Cafe in the Morrocan pavilion. I always get the vegetarian platter: falafel, tangierine couscous salad, hummus, tabouleh, lentil salad and marinated olives. It is plentiful, different and very satisfying. We eat there at least once on every trip. They also have chicken and lamb platters for the non-veg members of your party.
It kind of depends on whether you are in Future World at mealtime, or if you've already moved on to the World Showcase. Can't go wrong with either of these choice in my opinion.