This place is a little out of the way for me, I live near Atwood, but it's definitely worth the trip. Their sandwiches and baked goods are par excellence, they have no rivals in Madison. And they happen to have a good selection of vegetarian friendly fare. Plus the service is great to boot. Even if you have no reason to go out to the North side you should still find the time to give Manna a try.
Notable choices: the Earthly Delights and Ozy Tuna sandwhiches. Both the couscous and new potato sides are excellent and you can't go wrong with any of their baked goods.