Soak wooden skewers in water, and preheat barbecue to high; adjust to medium after about 15 minutes. Meanwhile, combine lime juice, cilantro, garlic, jalapeño pepper, cumin, and a little olive oil in a bowl. Add shrimp and toss to evenly coat.
When barbecue is hot, skewer shrimp and place on grill; cook about 4 minutes on each side or until shrimp are opaque.
Warm taco shells, then assemble. Fill each with a few shrimp and top with yogurt, salsa, lettuce, avocado, and more cilantro, if you wish.
Per serving: 416 calories, 36 g protein, 19 g total fat, 3 g saturated fat, 297 mg cholesterol, 28 g carbohydrates, 7 g fibre.