It's raining. Or it's cold. Or it's just one of those days. The kids are stuck indoors. What to do? What to do is to reach for Linda Hetzer's "Rainy Days and Saturdays," a family lifesaver of 160 engaging activities that can all be easily done using stuff from around the house and with little or no parental supervision. Kids can build a volcano and make it erupt. Plan a carnival. Write a letter in one-time code. Publish a family newspaper. Build a...