The standard advice: Drive your baby around the block.
Why it works: You're actually combining steady motion and white noise, so it makes sense that a car ride can do the trick. But it's hardly convenient at 2:30 a.m.
How moms add their own twist: Baby-equipment manufacturers do a brisk business selling vibrating bouncy seats, but many moms make their own versions of the white-noise-movement combo. Cheri Schulzke, a Pleasant Grove, Utah, mom of four, turned to her clothes dryer whenever her babies wouldn't stop fussing. "I put the bouncy seat on top of a towel on the dryer, turned it on, and watched it work its magic. They loved the movement, the hum, and the warmth," she says. (Stay close by if you try this with your baby; the seat may bounce around.)
Sometimes even the notion of motion works. Deborah Phillips spent a lot of time driving her daughter, Megan, 6 weeks old, around the block of their Snohomish, Washington, home to calm her down enough to sleep. But late one desperate night, she simply brought the car seat inside and set it on the living room floor. "She nestled right in and fell sound asleep," Phillips says. "I could've saved a lot of gas if I'd thought of this earlier!"