Prepare couscous according to package directions, omitting salt and fat. Set aside.
While couscous is standing, prepare raita. Combine cucumber and next 5 ingredients (cucumber through garlic) in a small bowl; cover and chill.
Prepare broiler or grill.
To prepare the kebabs, combine lamb, curry, 1 teaspoon oil, sugar, 1/2 teaspoon salt, and red pepper in a medium bowl; toss well. Combine 1 teaspoon oil, bell pepper, and tomatoes in a bowl; toss well. Thread lamb, bell pepper, and tomatoes alternately onto 4 (10-inch) skewers.
Place kebabs on broiler pan or grill rack coated with cooking spray; cook 7 minutes on each side or until done. Serve kebabs with raita and couscous.