Cook onion, garlic, cumin and pepper flakes in oil in 4-qt. saucepot over medium heat until onion is tender, about 3 minutes; remove from heat.
Puree 2 cans beans and their liquid in batches with chicken broth in electric blender; add to pot. Stir in remaining beans, salsa and lime juice.
Heat mixture to boil; reduce heat to low. Simmer for 30 minutes. Ladle 1 cup soup into bowl; top with dollop of yogurt. Serve hot with crackers.
Per serving (1 cup soup, 5 crackers): 284 calories, 14 g protein, 46 g carbohydrate, 4 g total fat,
0 g saturated fat, 0 mg cholesterol, 807 mg sodium, 6 g dietary fiber.