Bring a pot of water to a boil. Place snap peas in pot, and cook 1 to 2 minutes. Drain, rinse under cold water, and set aside.
Place about 1 1/2 tablespoons raspberries in a strainer over a bowl, and crush with a wooden spoon. Discard pulp. Mix vinegar, olive oil, sugar, salt, and pepper with the strained raspberry juice.
In a large bowl, gently toss the dressing with the snap peas, remaining raspberries, and blueberries. Cover, and chill at least 30 minutes in the refrigerator. Toss with greens just before serving.