In a small bowl, stir together soy sauce, vinegar, peanut butter, ginger, garlic and curry powder. Whisk in 1 tablespoon hot water until smooth. Set aside.
Bring a large pot of lightly salted water to a boil over high heat. Add broccoli, cauliflower, and carrots. Cook 2 minutes; add zucchini and squash and cook additional 2 minutes. Drain and rinse under cold water. Place in a large bowl and gently toss with half the sauce. Let stand 1 hour.
Thread vegetables onto skewers. Serve at room temperature with the remaining sauce.
