Preheat oven to 400 degrees F.
Heat 1 tablespoon of olive oil in a skillet and add tomatoes. Cook until tomatoes are softened. Add salt, to taste.
Spoon cooked tomatoes evenly over English muffin halves. In a skillet, saute eggplant and onions in 1 tablespoon of olive oil. Add squash and zucchini and cook until tender. Do not over cook, since they will cook some more in the oven. Add salt and pepper to taste. Spoon sauteed vegetables evenly over the tomatoes. Sprinkle each mini pizza with balsamic vinegar. Top with mozzarella and feta cheese. Sprinkle pizza with Greek seasoning and basil.
Bake 25 minutes, or until cheese is melted and crust is lightly browned.