Gently squeeze tomatoes to remove juices, then chop. Heat 3 tablespoons oil in heavy large saucepan over medium heat. Add onion and sauté until tender, about 5 minutes. Add garlic and sauté until soft, about 4 minutes. Add dried red pepper and stir 20 seconds. Mix in tomatoes and simmer until sauce thickens, stirring frequently, about 5 minutes. Season with salt and pepper. Stir in half of marjoram and half of parsley. Add clams to sauce. Cover and cook sauce until clams open, about 5 minutes.
Meanwhile, cook linguine in large pot of boiling salted water until just tender but still firm to bite. Drain well. Transfer to large bowl. Add remaining 1 tablespoon oil and toss to coat. Pour clams and sauce over, discarding any clams that do not open. Sprinkle with remaining chopped fresh herbs.
