Heat peanut oil in large non-stick skillet over medium-high heat. Add ginger and stir 30 seconds.
Add broccoli, carrot and celery and saute 5 minutes.
Add white parts of green onions, zucchini, yellow squash, bell pepper and sherry and saute until vegetables are crisp-tender, about 3 minutes longer.
Add tofu and stir gently until heated through, about 2 minutes.
Season to taste with salt and pepper.
Chinese Peanut Sauce: Mix peanut butter, soy sauce and garlic in medium bowl. Whisk in 1/2 cup hot water. Add remaining ingredients; whisk to blend. Season with salt and pepper. Let stand at room temperature 1 hour or cover and refrigerate up to 1 day. Makes about 1 3/4 cups.
Place spaghetti in large bowl. Add Chinese Peanut Sauce and toss to coat. Transfer to platter.
Top with vegetable mixture. Sprinkle with peanuts and chopped green parts of green onions.